Whether Java is a pass value or a reference

All Java method arguments are passed by value. However, Java does manipulate objects by reference, and all object variables themselves are. (Excerpt from references Alaxy.com:8080/interview/index.jsp? INTV=18)

The parameters of all methods in
Java are passed values. However, Java does manipulate objects by reference, and all object variables themselves are references.





originally all methods are passed values, there is no reference to the said!





give a few examples to see:





Example 1:


public class TestRef1 {


public static void Test (StringBuffer str) {


str = new StringBuffer (", world!");


}


public static void Main (string[] args) {


StringBuffer string = new StringBuffer ("Hello");


test (string);


System.out.println (string);


}


}


Run Result: Hello





Example 2:


public class TestRef2 {


public static void Test (String str) {


str = ", world!";


}


public static void Main (string[] args) {


string = new String ("Hello");


test (string);


System.out.println (string);


}


}


Run Result: Hello





Example 3:


public class TestRef3 {


public static void Test (StringBuffer str) {


str.append (", world!");


}


public static void Main (string[] args) {


StringBuffer string = new StringBuffer ("Hello");


test (string);


System.out.println (string);


}


Run Result: Hello, world!





first of all I think: The above three examples are the values, no reference.





Second, we think:


1, different references can point to the same object;


2, the value of the String object itself is immutable (like B = "world"; b = A; this does not change the value of the object of "world", but rather changes the value of its reference B to point to another String object a);


3, "=" is an assignment operator. The assignment modifies the object reference, not the object itself.





according to the above,


1, str = ", world!"; and str = new StringBuffer (", world!"); are assignment operations that modify the reference of the object Str to point to a new object without changing the object itself (here is ", world!" and new StringBuffer (", world!") ）。 So string is not affected by it.


2, Str.append (", world!"); This changes the object itself, not the object reference.





above are personal views, please correct me!