Confusion about new Integer () and new int [3]? ?

淮南一叶

1. I wrote a class myself, the code is as follows:
public class Test {
private final int i;
public Test (int i) {
// TODO Auto-generated constructor stub
this.i = i;
}

/ **
* @param args
* /
public static void main (String [] args) {
// TODO Auto-generated method stub
System.out.println (new Test (123));
System.out.println (new Integer (123));

}

}
Why System.out.println (new Test (123)); The result is Test @ 35ce36
The result of System.out.println (new Integer (123)); is 123? . . .

2.int [] j = new int [3]; is int [] a class? Why is new int [3] possible?


Thank you for your guidance. . . . . .

sunjingyao

Personal understanding. The general custom class, if output directly, will output the memory address of this object similar to Test @ 35ce36. And these wrapper classes will output the value it represents, I have not thought deeply

catmay

You did not override the toString () method, System.out.println (par) will call the toString () method of par.
public class Test {
private final int i;
public Test (int i) {
// TODO Auto-generated constructor stub
this.i = i;
}
public String toString () {
StringBuffer tmp = new StringBuffer ();
tmp.append (i);
return tmp.toString ();
}
/ **
* @param args
* /
public static void main (String [] args) {
// TODO Auto-generated method stub
System.out.println (new Test (123));
System.out.println (new Integer (123));

}

}

This will come out,
Ha ha!

catmay

int [] j = new int [3]; is an array of integers that can be put into 3 integers.

淮南一叶

catmay, I know that new int [3] is an array of integers. I want to know, is int [] a class? Why else can it be new?

tankingty

1 System.out.println (new Test (123)); In the new test (123) you are printing a class, it will call the "default" toString method, if you want to print the desired result, you need to override toString method.

2 int [] j = new int [3]; indicates that an int array j with 3 elements is defined

Ha ha, I have n’t looked at these basics for a long time, I may have forgotten it, so I understand it

淮南一叶

Brothers may have misunderstood what I mean. I know that int [] j = new int [3]; indicates that an int-type array j with 3 elements is defined. What I want to ask is: only when int [] is a class When you can create an object of it? But is int [] an object? Why can't I see its source code? confused. . . . . . .

sunjingyao

I think that's just one way to initialize the array

vg2321vbcj

All arrays are a class. You can use the isArray method of the Class class to determine whether an object is an array.