equals 和 == 区别

equals 比较两个字符串中的字符是否相等

== 比较两个字符串对象的地址是否相同

// An highlighted block
class Dog {
    public String name;
    Dog(String name){
        this.name =name;
    }
}

/**
 *  equals 比较两个字符串中的字符是否相等
 *  == 比较两个字符串对象的地址是否相同
 */
public class Demo {
    public static void main(String[] args){
        Dog dog1 = new Dog("xiaohuang");
        Dog dog2 = new Dog("xiaohuang");
        System.out.println(dog1 == dog2);             //flase
        //Dog类没有重写toString方法
        System.out.println(dog1.equals(dog2));          //flase

        String str1 = new String("abc");
        String str2 = new String("abc");
        System.out.println(str1 == str2);       //flase
        //String 类的equals 重写了toString方法
        System.out.println(str1.equals(str2));     //ture

        String s1 = "xiaohuang";
        String s2 = "xiaohuang";
        System.out.println(s1 == s2);    //ture
        System.out.println(s1.equals(s2));       //ture


        String s3 = dog1.toString();
        String s4 = dog2.toString();
        System.out.println(s3 == s4);                  //flase
        System.out.println(s3.equals(s4));            //flase

        Integer x = 5;
        System.out.println(x.toString());        //5
        System.out.println(Integer.toString(12));           //12

        String s7 = new String("hello");//s7 new了对象
        String s6 ="hello";//s6直接赋值
        System.out.println(s7 == s6);           //false
        System.out.println(s7.equals(s6));          //true
    }
}