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java结果输出,知其所以然

 
阅读更多
代码输出结果是什么?为什么会出现这种结果?
代码一
public class ParentTest {
	public ParentTest(){
		System.out.println("Parent Constructor invoked");
	}
	static{
		System.out.println("parent static invoked");
	}
	
	{
		System.out.println("parent invoked");
	}
}
public class ChildrenTest extends ParentTest{
	public ChildrenTest(){
		System.out.println("Children Constructor invoked");
	}
	static{
		System.out.println("Children static invoked");
	}
	
	{
		System.out.println("Children invoked");
	}
	public static void main(String[] args) {
		new ChildrenTest();
	}
}
代码二:true or false
public class MyTest1 {
	private String str;
	public MyTest1(String str){
		this.str=str;
	}
	public static void main(String[] args) {
		MyTest1 m1=new MyTest1("hello");
		MyTest1 m2=new MyTest1("hello");
		System.out.println(m1.equals(m2));
	}
}
代码三:true or false
public class MyTest1 {
	public static void main(String[] args) {
	System.out.println(Integer.valueOf(323)==Integer.valueOf(323));
	System.out.println(Integer.valueOf(23)==Integer.valueOf(23));
	}
}
代码四:
public class MyTest1 {
	private static int a;
	public MyTest1(){
		System.out.println("a="+(++a));
	}
	public void test(){
		int a=5;
		System.out.println("a="+a);
	}
	public void test2(){
		a=5;
		System.out.println("a="+a);
	}
	public static void main(String[] args) {
		new MyTest1();
		new MyTest1();
		new MyTest1().test();
		System.out.println(a);
		new MyTest1().test2();
		System.out.println(a);
	}
}
代码五:
public class Parent {
	public Parent(String name){
		System.out.println(name);
	}
}
public class Children extends Parent{
	public Children(String name){
		System.out.println(name);
	}
	
	public static void main(String[] args) {
		new Children("hello");
	}
}



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