String类的replace（）方法

Question

在此代码段中创建了多少个对象？

String x = "xyz"; // #1
x.toUpperCase(); /* Line 2 */ #2
String y = x.replace('Y', 'y'); //Will here new object is created or not?
y = y + "abc"; // #3 ?
System.out.println(y);

三。我想..？

Answer 1

  

创建了多少个对象？

// "xyz" is interned , JVM will create this object and keep it in String pool
String x = "xyz";
// a new String object is created here , x still refers to "xyz" 
x.toUpperCase(); 
// since char literal `Y` is not present in String referenced by x ,
// it returns the same instance referenced by x 
String y = x.replace('Y', 'y'); 
//  "abc" was interned and y+"abc" is a new object
y = y + "abc";  
System.out.println(y);

此语句返回对同一String对象x：

的引用

String y = x.replace('Y', 'y'); 

查看documentation：

  

如果字符oldChar未出现在此String对象表示的字符序列中，则返回对此String对象的引用。否则，将创建一个表示字符序列的新String对象与此String对象表示的字符序列相同，只是每次出现的oldChar都被newChar的出现替换。