题目内容

方法重载，并理解int型与char关系class Test{int compute( int a,int b ){return b-a;}String compute(String s1,String s2){return s1+s2;}public static void main(String args[ ]){Test t=new Test ( );char ch1='a';char ch2='b';System.out.println(t.compute(ch1,ch2));}}程序运行结果

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静态成员变量是共享的，非静态成员变量各对象独立class A {int n;static int m;public A(int n,int m) {this.n=n;this.m=m;}}class Test{public static void main(String args[ ]){A a1=new A(10,11);A a2=new A(20,21);System.out.println("a1:n="+a1.n+",m="+a1.m);System.out.println("a2:n="+a2.n+",m="+a2.m);}}程序运行结果：

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非静态方法被子类重写，上转型对象调用的是子类重写的方法，静态方法被子类重写，上转型对象调用的仍然是父类定义的静态方法。class SuperClass {void method() {System.out.println("SuperClass:method");}static void methodStatic() {System.out.println("SuperClass:methodStatic");}}class SubClass extends SuperClass {void method() {System.out.println("SubClass:method");}static void methodStatic() {System.out.println("SubClass:methodStatic");}}public class Test {public static void main(String[] args) {SuperClass a = new SubClass();a.method();a.methodStatic();}}程序运行结果：

String字符串是不可修改的，它的连接、取子串、替换都会生成新的字符串，原子符串不变public class Test{ public static void main(String args[]){String str="ABCDEF";str.substring(3);str.concat("XYZ");System.out.print(str);}}程序运行结果：