public class SingleTest {
	public SingleTest instance = new SingleTest();
	
	private SingleTest(){
		
	}
	
	public static void main(String[] args) {
		SingleTest test1 = new SingleTest().instance;
		System.out.println(test1.hashCode());
	}
}

package com.huawei.test;

public class AHEADInit {
	int j = init_j(i); //这里编译报错
	int i = 10;
	private int init_j(int i2) {
		return i2*i2;
	}
}

public static void main(String[] args) throws Exception{
	    File file = new File("");
	    System.out.println(System.getProperty("user.dir"));
	    System.out.println(System.getProperty("user.home"));
	    System.out.println(file.getAbsolutePath());
//		testByJNI();
	}
上面的代码执行路径证实了eclipse对目录src和bin目录进行了过滤，如果用eclipse执行和cmd命令行执行结果是不相同的。
1.在eclipse下面执行得到的路径D:\checkout\code
2.在cmd下面执行得到的路径是D:\checkout\code\bin

package com.huawei.test;

public class GCInvocateTest {

	@Override
	protected void finalize() throws Throwable {
		System.out.println("clean up glash");
		super.finalize();
	}

	public static void main(String[] args) {
		GCInvocateTest gc = new GCInvocateTest();
		gc = null;
		System.gc();
		System.out.println("1");
		System.gc();
	}
}

package com.huawei.test;

import java.util.HashMap;

public class HashTest {
	public static void main(String[] args) {
		getSize1();
		getSize2();
	}
	
	public static void getSize1(){
		HashMap<Object, String> instance = new HashMap<Object, String>();
		instance.put(new String(), "xx");
		instance.put(new String(), "xx");
		System.out.println(instance.size());
	}
	
	public static void getSize2(){
		HashMap<Object, String> instance = new HashMap<Object, String>();
		instance.put(new HashObject(), "xx");
		instance.put(new HashObject(), "xx");
		System.out.println(instance.size());
	}
	
	private static class HashObject{

	}
}

父类：
package com.huawei.test;

public class Parent {
	protected String name = "parent";
	protected String school = "grade_school";
	
	public void printName(){
		System.out.println(name);
	}
}
子类：
package com.huawei.test;

public class Child extends Parent{
	private String name = "child";
	private String school = "colleage_school";
	
	public static void main(String[] args) {
		Parent parent = new Child();
		parent.printName();
		System.out.println(parent.school);
	}
	@Override
	public void printName(){
		System.out.println(name);
	}
}
打印结果________________?

public static void main(String[] args){
		printWriterTest();
		printStreamTest();
	}
	
	public static void printWriterTest(){
		PrintWriter pw = new PrintWriter(System.out);
		pw.print("中国");
		pw.close();
	}
	public static void printStreamTest(){
		System.out.println("中国");
	}