201Xjava基础面试题优秀word范文 20页.docx
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201Xjava基础面试题优秀word范文 20页.docx
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201Xjava基础面试题
篇一:
201Xjava面试,基础题目
1.Java基础部分···················································································································3
1、一个".java"源文件中是否可以包括多个类(不是内部类)?
有什么限制?
···········4
2、Java有没有goto?
···········································································································4
3、说说&和&&的区别。
·····································································································4
4、在JAVA中如何跳出当前的多重嵌套循环?
·······························································4
5、switch语句能否作用在byte上,能否作用在long上,能否作用在String上?
······5
6、shorts1=1;s1=s1+1;有么错?
shorts1=1;s1+=1;有什么错?
·································5
7、char型变量中能不能存贮一个中文汉字?
为什么?
·····················································6
8、用最有效率的方法算出2乘以8等於几?
···································································6
9、请设计一个一百亿的计算器·························································································6
10、使用final关键字修饰一个变量时,是引用不能变,还是引用的对象不能变?
··8
11、"=="和equals方法究竟有什么区别?
·······································································8
12、静态变量和实例变量的区别?
···················································································9
13、是否可以从一个static方法内部发出对非static方法的调用?
····························10
14、Integer与int的区别··································································································10
15、Math.round(11.5)等於多少?
Math.round(-11.5)等於多少?
·····································11
16、下面的代码有什么不妥之处?
···················································································11
17、请说出作用域public,private,protected,以及不写时的区别···························11
18、Overload和Override的区别。
Overloaded的方法是否可以改变返回值的类型?
1220、接口是否可继承接口?
抽象类是否可实现(implements)接口?
抽象类是否可继承具体类(concreteclass)?
抽象类中是否可以有静态的main方法?
····································14
21、写clone()方法时,通常都有一行代码,是什么?
·················································14
22、面向对象的特征有哪些方面·····················································································14
23、java中实现多态的机制是什么?
··············································································16
24、abstractclass和interface有什么区别?
····································································16
25、abstract的method是否可同时是static,是否可同时是native,是否可同时是synchronized?
······················································································································18
27、内部类可以引用它的包含类的成员吗?
有没有什么限制?
·································21
28、AnonymousInnerClass(匿名内部类)是否可以extends(继承)其它类,是否可以implements(实现)interface(接口)?
·····················································································22
29、super.getClass()方法调用···························································································22
30、String是最基本的数据类型吗?
·················································································23
31、Strings="Hello";s=s+"world!
";这两行代码执行后,原始的String对象中的内容到底变了没有?
·················································································································23
32、是否可以继承String类?
····························································································24
33、Strings=newString("xyz");创建了几个StringObject?
二者之间有什么区别?
·····25
35、如何把一段逗号分割的字符串转换成一个数组?
···················································26
36、数组有没有length()这个方法?
String有没有length()这个方法?
·························26
37、下面这条语句一共创建了多少个对象:
Strings="a"+"b"+"c"+"d";························26
38、try{}里有一个return语句,那么紧跟在这个try后的finally{}里的code会不会被执行,什么时候被执行,在return前还是后?
·······························································27
39、下面的程序代码输出的结果是多少?
·····································································28
40、final,finally,finalize的区别。
····················································································30
41、运行时异常与一般异常有何异同?
·········································································31
42、error和exception有什么区别?
················································································31
43、Java中的异常处理机制的简单原理和应用。
·························································31
44、请写出你最常见到的5个runtimeexception。
······················································32
45、JAVA语言如何进行异常处理,关键字:
throws,throw,try,catch,finally分别代表什么意义?
在try块中可以抛出异常吗?
···········································································32
46、java中有几种方法可以实现一个线程?
用什么关键字修饰同步方法?
stop()和suspend()方法为何不推荐使用?
·····················································································32
47、sleep()和wait()有什么区别?
·····················································································34
48、同步和异步有何异同,在什么情况下分别使用他们?
举例说明。
·····················37
49.下面两个方法同步吗?
(自己发明)······································································38
50、多线程有几种实现方法?
同步有几种实现方法?
·····················································38
51、启动一个线程是用run()还是start()?
.·····································································39
52、当一个线程进入一个对象的一个synchronized方法后,其它线程是否可进入此对象的其它方法?
···················································································································39
53、线程的基本概念、线程的基本状态以及状态之间的关系·····································39
54、简述synchronized和java.util.concurrent.locks.Lock的异同?
·······························40
55、设计4个线程,其中两个线程每次对j增加1,另外两个线程对j每次减少1。
写出程序。
·····························································································································42
56、子线程循环10次,接着主线程循环100,接着又回到子线程循环10次,接着再回到主线程又循环100,如此循环50次,请写出程序。
············································45
57、介绍Collection框架的结构·······················································································52
58、Collection框架中实现比较要实现什么接口····························································53
59、ArrayList和Vector的区别·························································································53
61、List和Map区别?
······································································································54
62、List,Set,Map是否继承自Collection接口?
······························································54
63、List、Map、Set三个接口,存取元素时,各有什么特点?
··································54
64、说出ArrayList,Vector,LinkedList的存储性能和特性···············································56
65、去掉一个Vector集合中重复的元素········································································56
66、Collection和Collections的区别。
···········································································56
67、Set里的元素是不能重复的,那么用什么方法来区分重复与否呢?
是用==还是equals()?
它们有何区别?
····································································································57
69、两个对象值相同(x.equals(y)==true),但却可有不同的hashcode,这句话对不对?
·············································································································································58
70、TreeSet里面放对象,如果同时放入了父类和子类的实例对象,那比较时使用的是父类的compareTo方法,还是使用的子类的compareTo方法,还是抛异常!
····58
71、说出一些常用的类,包,接口,请各举5个·························································60
72、java中有几种类型的流?
JDK为每种类型的流提供了一些抽象类以供继承,请说出他们分别是哪些类?
·····································································································60
74、什么是java序列化,如何实现java序列化?
或者请解释Serializable接口的作用。
·············································································································································62
75、描述一下JVM加载class文件的原理机制?
·····························································63
1.Java基础部分基础部分的顺序:
基本语法,类相关的语法,内部类的语法,继承相关的语法,异常的语法,线程的语法,集合的语法,io的语法,虚拟机方面的语法。
1、一个".java"源文件中是否可以包括多个类(不是内部类)?
有什么限制?
可以有多个类,但只能有一个public的类,并且public的类名必须与文件名相一致。
2、Java有没有goto?
java中的保留字,现在没有在java中使用。
3、说说&和&&的区别。
&和&&都可以用作逻辑与的运算符,表示逻辑与(and),当运算符两边的表达式的结果都为true时,整个运算结果才为true,否则,只要有一方为false,则结果为false。
&&还具有短路的功能,即如果第一个表达式为false,则不再计算第二个表达式,例如,对于if(str!
=null&&!
str.equals(“”))表达式,当str为null时,后面的表达式不会执行,所以不会出现NullPointerException如果将&&改为&,则会抛出NullPointerException异常。
If(x==33&++y>0)y会增长,If(x==33&&++y>0)不会增长
&还可以用作位运算符,当&操作符两边的表达式不是boolean类型时,&表示按位与操作,我们通常使用0x0f来与一个整数进行&运算,来获取该整数的最低4个bit位,例如,0x31&0x0f的结果为0x01。
备注:
这道题先说两者的共同点,再说出&&和&的特殊之处,并列举一些经典的例子来表明自己理解透彻深入、实际经验丰富。
4、在JAVA中如何跳出当前的多重嵌套循环?
在Java中,要想跳出多重循环,可以在外面的循环语句前定义一个标号,然后在里层循环体的代码中使用带有标号的break语句,即可跳出外层循环。
例如,
ok:
for(inti=0;i<10;i++){
for(intj=0;j<10;j++){
System.out.println(“i=”+i+“,j=”+j);
if(j==5)breakok;
}
}
另外,我个人通常并不使用标号这种方式,而是让外层的循环条件表达式的结果可以受到里层循环体代码的控制,例如,要在二维数组中查找到某个数字。
intarr[][]={{1,2,3},{4,5,6,7},{9}};booleanfound=false;
for(inti=0;i found;i++){ for(intj=0;j System.out.println(“i=”+i+“,j=”+j); if(arr[i][j]==5){ found=true; break; } } } 5、switch语句能否作用在byte上,能否作用在long上,能否作用在String上? 在switch(expr1)中,expr1只能是一个整数表达式或者枚举常量(更大字体),整数表达式可以是int基本类型或Integer包装类型,由于,byte,short,char都可以隐含转换为int,所以,这些类型以及这些类型的包装类型也是可以的。 显然,long和String类型都不符合switch的语法规定,并且不能被隐式转换成int类型,所以,它们不能作用于swtich语句中。 6、shorts1=1;s1=s1+1;有么错? shorts1=1;s1+=1;有什么错? 对于shorts1=1;s1=s1+1;由于s1+1运算时会自动提升表达式的类型,所以结果是int型,再赋值给short类型s1时,编译器将报告需要强制转换类型的错误s1=(short)s1+1。 对于shorts1=1;s1+=1;由于+=是java语言规定的运算符,java编译器会对它进行特殊处理,因此可以正确编译。 篇二: Java基础编程练习题(50题及答案)201X 201X年Java基础编程经典练习题50道 【程序1】 题目: 古典问题: 有一对兔子,从出生后第3个月起每个月都生一对兔子,小兔子长到第三个月后每个月又生一对兔子,假如兔子都不死,问每个月的兔子总数为多少? //这是一个菲波拉契数列问题 publicclasslianxi01{ publicstaticvoidmain(String[]args){ System.out.println("第1个月的兔子对数: 1"); System.out.println("第2个月的兔子对数: 1"); intf1=1,f2=1,f,M=24; for(inti=3;i<=M;i++){ f=f2; f2=f1+f2; f1=f; System.out.println("第"+i+"个月的兔子对数: "+f2); } } } 【程序2】 题目: 判断101-200之间有多少个素数,并输出所有素数。 程序分析: 判断素数的方法: 用一个数分别去除2到sqrt(这个数),如果能被整除,则表明此数不是素数,反之是素数。 publicclasslianxi02{ publicstaticvoidmain(String
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