String两种实例化区别

public class StringTest {
    public static void main(String[] args) {
        String s1 = new String("abc");//构造器实例化，声明在堆
        String s2 = new String("abc");

        String s3 ="abc";//字面量实例化，声明在常量池
        String s4 ="abc";

        System.out.println(s1==s2);//false
        System.out.println(s3==s4);//true


        String s5 = s3+s4;//变量声明在栈
        String s6 = "abcabc"//常量池
        System.out.println(s5==s6);//false

        String s7 = "abc"+"abc";//常量池
        System.out.println(s7==s6);//true
        System.out.println(s7==s5);//false
    }
}