recently, I have been studying some basics. I have seen the constant pool and String.intern method in Java. I have also found some sample code on the Internet to run on my own machine, but I have found a strange problem, such as the following code:

// -sharp0
String str1 = new String("0") + new String("0");
str1.intern();
String str2 = "00";
System.out.println(str1 == str2); // true
System.out.println(str1.equals(str2)); // true

// -sharp1
String str1 = new String("1") + new String("1");
str1.intern();
String str2 = "11";
// 
System.out.println(str1 == str2); //  false        
// hashCode
System.out.println(str1.hashCode() == str2.hashCode()); // true
System.out.println(str1.equals(str2)); // true


// -sharp2
String str1 = new String("2") + new String("2");
str1.intern();
String str2 = "22";

System.out.println(str1 == str2); // true        
System.out.println(str1.equals(str2)); // true

I don"t understand why when two new String ("1") + new String ("1") add variables intern , defining the same string will not point to the address in StringPool !

the above code -sharp1 is changed to write as follows:

// -sharp1-Update
String str1 = (new String("1") + new String("1")).intern();
String str2 = "11";
System.out.println(str1 == str2); //  true           
System.out.println(str1.equals(str2)); // true

can also find the corresponding citation in StringPool . This is a strange thing. Please give me some advice!