Whether the modification of basic type and reference type is valid

public class TestTransferValue {
    public void changeValue1(int age){// copy   3
        age = 30;// What is modified is also a copy 
    }
    public void changeValue2(Person person){
        person.setPersonName("xxx");
    }
    public void changeValue3(String str){
        str = "xxx";
    }
    public static void main(String[] args) {
        TestTransferValue test = new TestTransferValue();
        int age = 20; // （ For basic types ） original script   1 
        test.changeValue1(age);// Pass the copy in  2
        System.out.println("age----"+age); // At this moment, the output is the original   4

        Person person = new Person("abc");               
        test.changeValue2(person);
        System.out.println("personName----"+person.getPersonName());

        String str = "abc";  //abc In the constant pool 
        test.changeValue3(str);
        System.out.println("String----"+str);
    }
}
 result ：       age----20
            personName----xxx
            String----abc
        

Person person（ Point to person Type references ） = new Person(“abc”);（ example ）


Spread changeValue3 When it's inside str Point to abc,r then str="xxx" You need to find... From the constant pool first xxx, Create in constant pool if not found xxx, then str Point to xxx, At this time, the output is still output main Method str, It still points to abc, And new changeValue Inside str Equivalent to not using .

summary ： Pass the basic type unchanged , Transfer reference type change