java细节篇（==和equals的区别）

package test;

public class Test {

    public static void main(String[] args) {
        
        System.out.println("###############对象时比的都是地址################");
        TestObj t = new TestObj();
        TestObj t2 = new TestObj();
        System.out.println(t==t2);//false
        System.out.println(t.equals(t2));//false
        
        System.out.println("############基本类型[==]比的是值###########");
        int a=1;
        float b=1f;
        System.out.println(a==b);//true
        //  System.out.println(a.equals(b)); 写法错误
        
        System.out.println("##########Integer特殊(equals重写成比较值，但new时==还是比较地址)##########");
        Integer i1=0;
        Integer i2=0;
        System.out.println(i1==i2);//true
        System.out.println(i1.equals(i2));//true
        Integer i3 = new Integer(0);
        Integer i4 = new Integer(0);
        System.out.println(i3==i4);//false
        System.out.println(i3.equals(i4));//true
        System.out.println(i1==i3);//false
        System.out.println(i1.equals(i3));//true
        System.out.println(i4.equals(i2));//true
        int i5 = 0;
        System.out.println(i1.equals(i5));//true 和基本int类型比是比值
        System.out.println(i1==i5);//true 和基本int类型比也是比值
        System.out.println(i3.equals(i5));//true new的和基本int类型比是比值
        System.out.println(i3==i5);//true  new的和基本int类型比也是比值
        float f6 = 0f;//等同f6=0;
        System.out.println(i1.equals(f6));//false 注意结果不同说明equals的重写只是对int类型时是比值
        System.out.println(i1==f6);//true
        System.out.println(i3.equals(f6));//false 注意结果不同说明equals的重写只是对int类型时是比值
        System.out.println(i3==f6);//true  
        
        System.out.println("=======String特殊=======");
        String s1="a";
        String s2="a";
        System.out.println(s1==s2);
        System.out.println(s1.equals(s2));
        String s3 = new String("a");
        String s4 = new String("a");
        System.out.println(s3==s4);
        System.out.println(s3.equals(s4));
        System.out.println(s1==s3);
        System.out.println(s1.equals(s3));
        System.out.println(s4.equals(s2));
        
        
    }

}

/**
     * Compares this object to the specified object.  The result is
     * {@code true} if and only if the argument is not
     * {@code null} and is an {@code Integer} object that
     * contains the same {@code int} value as this object.
     *
     * @param   obj   the object to compare with.
     * @return  {@code true} if the objects are the same;
     *          {@code false} otherwise.
     */
    public boolean equals(Object obj) {
        if (obj instanceof Integer) {
            return value == ((Integer)obj).intValue();
        }
        return false;
    }