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Core Java interview questions


Total available count: 636
Subject - Java Technologies
Subsubject - Core Java
1
Can an interface have static methods in java?
2
Can a normal class have an abstract method in java?
3
Can constructor perform other tasks instead of initialization?
4
Can Method Local inner class access instance variable in java?
5
Can Method Local inner class access variable defined in the method in java?
6
Can muliple threads access simultaneously in the case of StringBuffer class in java?
7
Can Static nested class access non static member of outer class in java?
8
Can we access clone() method from outside the package in java?
9
Can we access clone() method from outside the package in java?
10
Can we change the value of String object once assigned in java?
11
Can we directly execute the normal inner class file with java command?
12
Can we execute a program without main() method in java?
13
Can we execute a program without main() method in java?
14
Can we handle Errors using try-catch block in java?
15
Can we include size of array at declaration in java?
16
Can we inherit constructor in java?
17
Can we instantiate abstract class in java?
18
Can we overload main() method?
19
Can we overload main() method?
20
Can we overridden Static methods in java?
21
Can we override final method in java?
22
Can we override private methods in java?
23
Can we shuffle the words public, static and void of main method in java?
24
Can we stop excecution of "finally" block in java?
25
Can we stop execution of finally block in java?
26
Can we use both this and super keywords in constructor?
27
Can we use final for constructor?
28
Can we use final for methods in an Interface?
29
Can we write main method in abstract class in java?
30
Can we write try block alone in java?
31
Can you differentiate abstract class and interface in java?
32
Can you give example for Checked Exception in java?
33
Can you give example for Error in java?
34
Can you give example for Exception in java?
35
Can you give example for nested interface in java?
36
Can you give example for UnChecked Exception in java?
37
Can you have virtual functions in Java?
38
Define Compile time polymorphism and give an example in java?
39
Define Run time polymorphism and give an example in java?
40
Describe object oriented programming and what is object ?
41
Describe what is java?
42
Differentiate between String and StringBuffer in java?
43
Differentiate between StringBuffer and StringBuilder in java?
44
Differentiate Checked and Unchecked Exceptions?
45
Differentiate Error and Exception in java?
46
Differentiate overloading and overriding in java?
47
Does java supports multiple inheritance or not and how?
48
From which version isEmpty() method of String class is available in java?
49
From which version isEmpty() method of String class is available in java?
50
From which version join() method of String class is available in java?
51
From which version of java,StringBuilder class is available?
52
From which version replace(CharSequence target, CharSequence replacement) method of String class is available in java?
53
From which version split() method of String class is available in java?
54
Give me some examples about Marked or Tagged Interfaces in java?
55
How can we overcome the variable hiding problem in java?
56
How can you create String object using new keyword with example?
57
How can you create String object using String literal with example?
58
How many access modifiers can be applied on Method Local inner class in java?
59
How many access modifiers can be applied on normal inner class?
60
How many classloaders are there and name them in Java?
61
How many methods are there in Runnable Interface in java?
62
How many type of variables available in java,mention them?
63
How many type of variables available in java, mention them?
64
How many types of access modifiers are available in java, mention them?
65
How many types of arrays available in java?
66
How many types of constructor in java and what are they?
67
How many types of Errors are available in java?
68
How many types of Exceptions are available in java?
69
How many types of polymorphism available in java?
70
How object can be created using Class.forName()in java?
71
How object can be created using Class.forName() in java?
72
How object can be created using clone() in java?
73
How object can be created using newinstance() in java?
74
How object can be created using newinstance() in java?
75
How object can be created using new keyword in java?
76
How object can be created using object deserialization in java?
77
How to get "this" for outer class if "this" is referencing inner class in java?
78
How to set JAVA_HOME or JRE_HOME environment variable in windows 7 and 8?
79
In case of Multidimensional array,is it compulsory to mention size limit of all dimensions?
80
In case of Multidimensional array, is it compulsory to mention size limit of all dimensions?
81
In how many ways object can be created in java?
82
In how many ways String object can be created in java?
83
In how many ways we can access static fields(variables or methods) in java?
84
In how many ways we can create Thread in java?
85
In how many ways we can declare single dimensional arrays in java?
86
In how many ways we can declare two dimensional arrays in java?
87
Is Error and Exception is same or different in java?
88
Is it compulsory for a abstract class to have abstract methods?
89
Is it compulsory for a subclass of abstract class to provide implementation of abstract method?
90
Is it necessary for a abstract class to provide method implementation when it implements interface?
91
Is it necessary for a class to provide all methods implementation when it implements interface?
92
Is it possible to instantiate abstract class in java?
93
Is it possible to instantiate interface in java?
94
Is java platform dependent or not?
95
Is java supports multiple inheritance?
96
Is static keyword can be applied to Class (Not Nested) in java?
97
Is static keyword can be applied to Constructor in java?
98
Is static keyword can be applied to Inner Class methods in java?
99
Is static keyword can be applied to interfaces in java?
100
Is static keyword can be applied to Method Local Inner Class in java?
101
Is there any difference if i use public static void main(String[] args) instead of public static void main(String args[])?
102
Is there any difference if i use public static void main(String[] args) instead of public static void main(String args[])?
103
Mainly how many types of inner class can be available in java?
104
Mention advantages of array in java?
105
Mention disadvantages of array in java?
106
Show me the syntax for declaration and instantiation of array in java?
107
Show me the syntax for declaration,instantiation and initialization of array in java?
108
String Object belongs to which package in java?
109
Suppose we have a class called Outer and with in it another class called Inner.what happen if we compile OuterClass file?
110
The equals() method of string class overrides which class method in java?
111
The method clone() throws which exception?
112
The method clone() throws which exception?
113
The method finalize() throws which exception?
114
The method finalize() throws which exception?
115
What are static methods available in string class in java?
116
What are the advantages of multi-threading in java?
117
What are the commonly used Constructors of Thread class in java?
118
What are the different states of thread in java?
119
What are the different type of constructors available in StringBuffer class in java?
120
What are the different type of constructors available in StringBuilder class in java?
121
What are the different type of constructors available in StringTokenizer class in java?
122
What are the different types of non access modifiers available in java?
123
What are the synchronized methods available in StringBuffer class in java?
124
What are the various values return by compareTo(String anotherString) method of string in java?
125
What do you know about Ananymous Inner Class in java?
126
What do you know about Anonymous Inner Class in java?
127
What do you know about array in java?
128
What do you know about Checked Exceptions in java?
129
What do you know about contravariant in java?
130
What do you know about covariant return type in java?
131
What do you know about de-serialization and de-serialize of object?
132
What do you know about Error in java?
133
What do you know about Exception in java?
134
What do you know about finally keyword in java?
135
What do you know about innerclass in java?
136
What do you know about inner class in java?
137
What do you know about Interface in Java?
138
What do you know about invariant in java?
139
What do you Know about Marked or Tagged Interface in java ?
140
What do you know about Method Local Inner class in java?
141
What do you know about multidimensional array in java?
142
What do you know about Multitasking and in how many ways of Multitasking can be acheived?
143
What do you know about Multithreading in java?
144
What do you know about native modifier in java?
145
What do you know about Nested interfaces in java?
146
What do you know about Normal Inner Class in java?
147
What do you know about overloading in java?
148
What do you know about serialize of object and serialization in java?
149
What do you know about serialize of object and serilization in java?
150
What do you know about Static Inner class in java?
151
What do you know about static method in java?
152
What do you know about Strictfp modifier in java?
153
What do you know about StringBuffer class in java?
154
What do you know about StringBuilder class in java?
155
What do you know about String class in java?
156
What do you know about StringTokenizer class in java?
157
What do you know about Synchronized non access modifier in java?
158
What do you know about Thread in java?
159
What do you know about transient Modifier in java?
160
What do you know about try and catch keywords in java?
161
What do you know about Unchecked Exceptions in java?
162
What do you know about variable hiding in java?
163
What do you know about volatile modifier in java?
164
What happen if main method is not declared as public,static and void in java?
165
What if the static modifier is removed from the signature of the main method?
166
What is CLASSPATH and is the purpose of it?
167
What is class variable(static variable) in java?
168
What is default capacity of StringBuffer() constructer of StringBuffer class?
169
What is default capacity of StringBuilder() constructer of StringBuilder class?
170
What is difference between static (class) method and instance method in java?
171
What is downcasting in java?
172
What is final class and give example for final in java?
173
What is function of currentThread() method of thread class in java?
174
What is function of getName() method of thread class in java?
175
What is function of getPriority() method of thread class in java?
176
What is function of join(long miliseconds) method of thread class in java?
177
What is function of join() method of thread class in java?
178
What is function of run() method of thread class in java?
179
What is function of setName(String name) method of thread class in java?
180
What is function of setPriority(int priority) method of thread class in java?
181
What is function of sleep(long miliseconds) method of thread class in java?
182
What is function of start() method of thread class in java?
183
What is immutable class and give an example?
184
What is instance variable in java?
185
What is java ClassLoader and function of it?
186
What is java virtual machine(JVM)?
187
What is java virtual machine(JVM)?
188
What is local variables in java?
189
What is meant by abstract class in java?
190
What is meant by abstract method in java?
191
What is meant by access modifier in java?
192
What is meant by Explicit Constructor Invocation in java?
193
What is meant by non access modifier in java?
194
What is mutable string and which are used to create mutable string in java?
195
What is object class in java?
196
What is object cloning in java?
197
What is returned by the method toString() in java?
198
What is returned by the method toString() in java?
199
What is the command to check java is properly installed in computer?
200
What is the difference between Abstraction and Encapsulation in java?
201
What is the difference between class and object in java?
202
What is the difference between creating string object using string literal and using new keyword in java?
203
What is the Difference between method Overloading and Overriding in java?
204
What is the difference between newinstance() method in Class.forName() method in java?
205
What is the difference between newinstance() method in Class.forName() method in java?
206
What is the difference between protected and default(no specifier) access modifier?
207
What is the difference between serialization and de-serialization in java?
208
What is the function of bootstrap classloader?
209
What is the function of Extensions class loader in java?
210
What is the function of System class loader in Java?
211
What is the importance of StringBuffer() constructor of StringBuffer class in java?
212
What is the importance of StringBuffer(int capacity) constructor of StringBuffer class in java?
213
What is the importance of StringBuffer(String str) constructor of StringBuffer class in java?
214
What is the importance of StringBuilder() constructor of StringBuilder class in java?
215
What is the importance of StringBuilder(int length) constructor of StringBuilder class in java?
216
What is the importance of StringBuilder(String str) constructor of StringBuilder class in java?
217
What is the importance of StringTokenizer(String str) constructor of StringTokenizer class in java?
218
What is the importance of StringTokenizer(String str, String delim, boolean returnValue) constructor of StringTokenizer class in java?
219
What is the importance of StringTokenizer(String str, String delim) constructor of StringTokenizer class in java?
220
What is the responsibility of class loader in Java?
221
What is the return type of append(String s) method of StringBuffer class in java?
222
What is the return type of append(String s) method of StringBuilder class in java?
223
What is the return type of capacity() method of StringBuffer class in java?
224
What is the return type of capacity() method of StringBuilder class in java?
225
What is the return type of charAt(int index) method of java.lang.String class in java?
226
What is the return type of charAt(int index) method of StringBuffer class in java?
227
What is the return type of charAt(int index) method of StringBuilder class in java?
228
What is the return type of compareTo(String anotherString) method of java.lang.String class in java?
229
What is the return type of concat(String str) method of java.lang.String class in java?
230
What is the return type of contains(CharSequence s) method of java.lang.String class in java?
231
What is the return type of countTokens() method of StringTokenizer class in java?
232
What is the return type of delete(int startIndex, int endIndex) method of StringBuffer class in java?
233
What is the return type of delete(int startIndex, int endIndex) method of StringBuilder class in java?
234
What is the return type of endsWith(String suffix) method of java.lang.String class in java?
235
What is the return type of ensureCapacity(int minimumCapacity) method of StringBuffer class in java?
236
What is the return type of ensureCapacity(int minimumCapacity) method of StringBuilder class in java?
237
What is the return type of equals(Object another) method of java.lang.String class in java?
238
What is the return type of format(Locale l, String format, Object... args) method of java.lang.String class in java?
239
What is the return type of format(String format, Object... args) method of java.lang.String class in java?
240
What is the return type of getBytes() method of java.lang.String class in java?
241
What is the return type of getBytes() method of java.lang.String class in java?
242
What is the return type of hasMoreElements() method of StringTokenizer class in java?
243
What is the return type of hasMoreTokens() method of StringTokenizer class in java?
244
What is the return type of indexOf(int ch, int fromIndex) method of java.lang.String class in java?
245
What is the return type of indexOf(int ch) method of java.lang.String class in java?
246
What is the return type of indexOf(String substring, int fromIndex) method of java.lang.String class in java?
247
What is the return type of indexOf(String substring) method of java.lang.String class in java?
248
What is the return type of insert(int offset, String s) method of StringBuffer class in java?
249
What is the return type of insert(int offset, String s) method of StringBuilder class in java?
250
What is the return type of intern() method of java.lang.String class in java?
251
What is the return type of intern() method of java.lang.String class in java?
252
What is the return type of isEmpty() method of java.lang.String class in java?
253
What is the return type of isEmpty() method of java.lang.String class in java?
254
What is the return type of join(CharSequence delimiter, CharSequence... elements) method of java.lang.String class in java?
255
What is the return type of lastIndexOf(int ch, int fromIndex) method of java.lang.String class in java?
256
What is the return type of lastIndexOf(int ch) method of java.lang.String class in java?
257
What is the return type of lastIndexOf(String substring, int fromIndex) method of java.lang.String class in java?
258
What is the return type of lastIndexOf(String substring) method of java.lang.String class in java?
259
What is the return type of length() method of java.lang.String class in java?
260
What is the return type of length() method of java.lang.String class in java?
261
What is the return type of length() method of StringBuffer class in java?
262
What is the return type of length() method of StringBuilder class in java?
263
What is the return type of nextElement() method of StringTokenizer class in java?
264
What is the return type of nextToken() method of StringTokenizer class in java?
265
What is the return type of nextToken(String delim) method of StringTokenizer class in java?
266
What is the return type of replaceAll(String regex, String replacement) method of java.lang.String class in java?
267
What is the return type of replace(char old, char new) method of java.lang.String class in java?
268
What is the return type of replace(CharSequence old, CharSequence new) method of java.lang.String class in java?
269
What is the return type of replace(int startIndex, int endIndex, String str) method of StringBuffer class in java?
270
What is the return type of replace(int startIndex, int endIndex, String str) method of StringBuilder class in java?
271
What is the return type of reverse() method of StringBuffer class in java?
272
What is the return type of reverse() method of StringBuilder class in java?
273
What is the return type of split(String regex, int limit) method of java.lang.String class in java?
274
What is the return type of split(String regex) method of java.lang.String class in java?
275
What is the return type of startsWith(String prefix) method of java.lang.String class in java?
276
What is the return type of substring(int beginIndex, int endIndex) method of java.lang.String class in java?
277
What is the return type of substring(int beginIndex, int endIndex) method of StringBuffer class in java?
278
What is the return type of substring(int beginIndex, int endIndex) method of StringBuilder class in java?
279
What is the return type of substring(int beginIndex) method of java.lang.String class in java?
280
What is the return type of substring(int beginIndex) method of StringBuffer class in java?
281
What is the return type of substring(int beginIndex) method of StringBuilder class in java?
282
What is the return type of toCharArray() method of java.lang.String class in java?
283
What is the return type of toLowerCase(Locale l) method of java.lang.String class in java?
284
What is the return type of toLowerCase() method of java.lang.String class in java?
285
What is the return type of toLowerCase() method of java.lang.String class in java?
286
What is the return type of toUpperCase(Locale l) method of java.lang.String class in java?
287
What is the return type of toUpperCase() method of java.lang.String class in java?
288
What is the return type of toUpperCase() method of java.lang.String class in java?
289
What is the return type of trim() method of java.lang.String class in java?
290
What is the return type of trim() method of java.lang.String class in java?
291
What is the return type of valueOf(boolean b) method of java.lang.String class in java?
292
What is the return type of valueOf(char[] c) method of java.lang.String class in java?
293
What is the return type of valueOf(double d) method of java.lang.String class in java?
294
What is the return type of valueOf(float f) method of java.lang.String class in java?
295
What is the return type of valueOf(int i) method of java.lang.String class in java?
296
What is the return type of valueOf(long l) method of java.lang.String class in java?
297
What is the return type of valueOf(Object o) method of java.lang.String class in java?
298
What is the visibility of private access modifier?
299
What is the visibility of public access modifier?
300
What is this keyword in java or importance of this keyword in java?
301
What is upcasting in java?
302
What is visibility of default(no specifier) access modifier?
303
What is visibility of protected access modifier?
304
What meant by final variable and how will we declare?
305
What the function of append(String s) method of StringBuffer class in java?
306
What the function of append(String s) method of StringBuilder class in java?
307
What the function of capacity() method of StringBuffer class in java?
308
What the function of capacity() method of StringBuilder class in java?
309
What the function of charAt(int index) method of StringBuffer class in java?
310
What the function of charAt(int index) method of StringBuilder class in java?
311
What the function of CharAt(int index) method of String class in java?
312
What the function of concat(String str) method of String class in java?
313
What the function of contains(CharSequence s) method of String class in java?
314
What the function of countTokens() method of StringTokenizer class in java?
315
What the function of delete(int startIndex, int endIndex) method of StringBuffer class in java?
316
What the function of delete(int startIndex, int endIndex) method of StringBuilder class in java?
317
What the function of endsWith(String suffix) method of String class in java?
318
What the function of endsWith(String suffix) method of String class in java?
319
What the function of ensureCapacity(int minimumCapacity) method of StringBuffer class in java?
320
What the function of ensureCapacity(int minimumCapacity) method of StringBuilder class in java?
321
What the function of equals(Object another) method of String class in java?
322
What the function of format(Locale l, String format, Object... args) method of String class in java?
323
What the function of format(String format, Object... args) method of String class in java?
324
What the function of getBytes() method of String class in java?
325
What the function of getBytes() method of String class in java?
326
What the function of hasMoreElements() method of StringTokenizer class in java?
327
What the function of hasMoreTokens() method of StringTokenizer class in java?
328
What the function of indexOf(int ch, int fromIndex) method of String class in java?
329
What the function of indexOf(int ch) method of String class in java?
330
What the function of indexOf(String substring, int fromIndex) method of String class in java?
331
What the function of indexOf(String substring) method of String class in java?
332
What the function of insert(int offset, String s) method of StringBuffer class in java?
333
What the function of insert(int offset, String s) method of StringBuilder class in java?
334
What the function of intern() method of String class in java?
335
What the function of intern() method of String class in java?
336
What the function of isEmpty() method of String class in java?
337
What the function of isEmpty() method of String class in java?
338
What the function of join(CharSequence delimiter, CharSequence... elements) method of String class in java?
339
What the function of lastIndexOf(int ch, int fromIndex) method of String class in java?
340
What the function of lastIndexOf(int ch) method of String class in java?
341
What the function of lastIndexOf(String substring, int fromIndex) method of String class in java?
342
What the function of lastIndexOf(String substring) method of String class in java?
343
What the function of length() method of StringBuffer class in java?
344
What the function of length() method of StringBuilder class in java?
345
What the function of length() method of String class in java?
346
What the function of length() method of String class in java?
347
What the function of nextElement() method of StringTokenizer class in java?
348
What the function of nextToken() method of StringTokenizer class in java?
349
What the function of nextToken(String delim) method of StringTokenizer class in java?
350
What the function of replaceAll(String regex, String replacement) method of String class in java?
351
What the function of replace(char old, char new) method of String class in java?
352
What the function of replace(CharSequence old, CharSequence new) method of String class in java?
353
What the function of replace(int startIndex, int endIndex, String str) method of StringBuffer class in java?
354
What the function of replace(int startIndex, int endIndex, String str) method of StringBuilder class in java?
355
What the function of reverse() method of StringBuffer class in java?
356
What the function of reverse() method of StringBuilder class in java?
357
What the function of split(String regex, int limit) method of String class in java?
358
What the function of split(String regex) method of String class in java?
359
What the function of split(String reg, int limit) method of String class in java?
360
What the function of startsWith(String prefix) method of String class in java?
361
What the function of substring(int beginIndex, int endIndex) method of StringBuffer class in java?
362
What the function of substring(int beginIndex, int endIndex) method of StringBuilder class in java?
363
What the function of substring(int beginIndex, int endIndex) method of String class in java?
364
What the function of substring(int beginIndex) method of StringBuffer class in java?
365
What the function of substring(int beginIndex) method of StringBuilder class in java?
366
What the function of substring(int beginIndex) method of String class in java?
367
What the function of toCharArray() method of String class in java?
368
What the function of toLowerCase(Locale l) method of String class in java?
369
What the function of toLowerCase() method of String class in java?
370
What the function of toLowerCase() method of String class in java?
371
What the function of toUpperCase(Locale l) method of String class in java?
372
What the function of toUpperCase() method of String class in java?
373
What the function of toUpperCase() method of String class in java?
374
What the function of trim() method of String class in java?
375
What the function of trim() method of String class in java?
376
What the function of valueOf(boolean b) method of String class in java?
377
What the function of valueOf(char[] c) method of String class in java?
378
What the function of valueOf(double d) method of String class in java?
379
What the function of valueOf(float f) method of String class in java?
380
What the function of valueOf(int i) method of String class in java?
381
What the function of valueOf(long l) method of String class in java?
382
What the function of valueOf(Object o) method of String class in java?
383
When will charAt(int index) method throws IndexOutOfBoundsException in java?
384
When will compareTo(String anotherString) method of string returns negative number in java?
385
When will compareTo(String anotherString) method of string returns positive number in java?
386
When will compareTo(String anotherString) method of string returns zero in java?
387
When will contains(CharSequence sequence) method of string returns false in java?
388
When will contains(CharSequence sequence) method of string returns true in java?
389
When will contains(CharSequence sequence) method throws NullPointerException in java?
390
When will equals(Object anotherObject) method of string returns false in java?
391
When will equals(Object anotherObject) method of string returns true in java?
392
When will isEmpty() method of string returns false in java?
393
When will isEmpty() method of string returns false in java?
394
When will isEmpty() method of string returns true in java?
395
When will isEmpty() method of string returns true in java?
396
When will split(String regex) method throws "PatternSyntaxException" in java?
397
When will String.format(String format, Object... args) method throws "IllegalFormatException" in java?
398
When will String.format(String format, Object... args) method throws "NullPointerException" in java?
399
When will String.join(CharSequence delimiter, CharSequence... elements) method throws "NullPointerException" in java?
400
When will substring(int startIndex, int endIndex) method throws "StringIndexOutOfBoundsException" in java?
401
When will we use final methods in java?
402
Where can Method local inner class can be instantiated in java?
403
Which can be used to overcome the immutable property of String in java?
404
Which class implements Extensions class loader?
405
Which class implements System Class Loader in java?
406
Which class is the superclass for every class in java?
407
Which class is the super class for every class in java?
408
Which environment variable points to java home directory?
409
Which exception does charAt() method of string throws in java?
410
Which exception does charAt() method of string throws in java?
411
Which exception does contains(CharSequence sequence) method of string throws in java?
412
Which exception does getBytes(String charsetName) method of string throws in java?
413
Which exception does split(String regex) method of string throws in java?
414
Which exception does substring(int startIndex, int endIndex) method of string throws in java?
415
Which Exception is thrown if try to use clone() method with implementing Cloneable interface in java?
416
Which Exception is thrown if try to use clone() method with implementing Cloneable interface in java?
417
Which exceptions does String.format() method throws in java?
418
Which exceptions does String.join(CharSequence delimiter, CharSequence... elements) method throws in java?
419
Which interfaces that String implements in java?
420
Which is an example for Polymorphism,overloading or overriding?
421
Which is an example for Polymorphism: overloading or overriding?
422
Which keyword helps to prevent overriden and inherit in java?
423
Which keywords are used when a class inherits interface and interface inherits interface in java?
424
Which latest version of java is in market and when it released?
425
Which member of the outer class can be accessed by inner class instance?
426
Which method is called by String.format(Locale locale, String format, Object... args) method when you do not specify the locale parameter?
427
Which method is invoked by the garbage collector before object is being garbage collected?
428
Which method is used to represent object as string in java?
429
Why Java does not support pointers?
430
Why main method is static in java?
431
Why String is immutable in java?
432
Why the main method in java is public ?
433
Why the main method in java is static?
434
Why the main method in java is void?
435
Will it create two objects If two strings have same value using String literal in java?
436
Write the code to create new object for normal inner class in java?
437
Write the syntax to use Ananymous Inner Class in java?
438
Write the syntax to use Anonymous Inner Class in java?