lukuijun1981的专栏

[code="java"]public class StringTest { public static void main(String[] args) { String str = new String("abc"); //语句(1) String str1 = "abc";//语句(2) String str2 = new ...

[code="java"]public class People{ String name; public People(String name){ this.name = name; } public String getName(){ return name; }}public class SetTest { public static void m...

[code="java"]interface I{}public class ArrayTest { public static void main(String[] args) { I[] i = new I[2]; }}[/code]问题1:上面的程序能否编译通过？并说明理由。解答:能编译通过。分析:对数组的认识，注意数组里面存放的不是对象，而...

[code="java"]public class Person { String name; public Person(String name){ this.name = name; } @Override public boolean equals(Object anObject){ //仿照String类的equals方法来写 if(this == a...

[code="java"]public class PublicStaticFinalTest { public static final String str = "abc";}[/code]问题:为什么对于一个public类型的终态的成员变量，一般都要声明为static的？解答:节省内存。分析:final是终态的，既然是终态的我们可以把它当作常量，一但赋值，它的值就不能去做任何...

[code="java"]public abstract final class AbstractFinalTest {}[/code]问题：上述代码能否编译通过？为什么？解答：不能编译通过。分析：它会报错,非法的修饰符组合abstract和final。分析:java采取什么策略导致abstract和final不能同时使用呢？是这样的:abstract修饰一个类表示这个类是抽象...

[code="java"]import java.io.IOException;public class ExceptionTryCatchTest { public void doSomething() throws IOException{ System.out.println("do somthing"); } public static void main(Strin...

[code="java"]public class ExceptionTypeTest { public void doSomething()throws ArithmeticException{ System.out.println(); } public static void main(){ ExceptionTypeTest ett = new ExceptionT...

[code="java"]public class ExceptionExecuteTest { public static void main(String[] args){ try { String s = null; return; } catch (RuntimeException e) { System.out.println("exception...

[code="java"]public class FinalReferenceTest { public static final StringBuffer sb = new StringBuffer(); public static void main(String[] args){ sb.append("hello"); }}[/code]问题1:上面的程序能否编译...

[code="java"]public class FinalOriginalTest { private final int a; private String name; public FinalOriginalTest(){ a = 3; } public FinalOriginalTest(String name){ this.name = name; ...

[code="java"]public class ReadOnlyClass { private String name = "hello"; public String getName(){ return name; }}[/code]问题：能否将ReadOnlyClass 类的一个对象，把它的name属性的值由hello改为world?如果能，请写出实现代码...

[code="java"]public class Parent{ public void output()throws NullPointerException{ System.out.println("parent"); }}public class Child extends Parent{ public void output() throws Exception...

[code="java"]class Parent{ static String name = "hello"; { System.out.println("parent block"); } static { System.out.println("parent static block"); } public Parent(){ System.out...

[code="java"]public class StaticVariableTest { private static StaticVariableTest svt = new StaticVariableTest();//语句(1) private static int count1;//语句(2) private static int count2 = 0;//语句(3) ...

[code="java"]public class Point{ private int x; private int y; public Point(int x,int y){ this.x = x; this.y = y; } public int getX() { return x; } public void setX(int x) { ...

题目:请说出hashCode方法,equals方法，HashSet，HasMap之间的关系？解答:策略,分析jdk的源代码:[code="java"] public HashSet() { map = new HashMap(); }[/code]1、HashSet底层是采用HashMap实现的。private transient HashMap map;是...