What are the characteristics of String class in java

Features:

(Recommended tutorial: java introductory tutorial)

1. The String class is modified by final. It cannot be inherited.

2. The underlying layer of the String class uses an array structure. Before jdk9, char[] was used, and after jdk9, byte[] was used.

3. Once a String object is created, it cannot be modified. A string constant pool is maintained at the bottom layer to achieve sharing.

Note: Every time an object of the String class is modified, a new object will be generated.

(Video tutorial recommendation: java video tutorial)

Splicing of String objects

String constants in the constant pool Strings in the constant pool Constant: The result is a string constant stored in the constant pool

String c = "a"+"b";
String ab = "ab";
System.err.println(ab==c); //输出true123

Variable constant pool: The result is a string constant stored in the heap

String a = "a";
String c = "a"+"b";
System.err.println(c==a+"b"); //输出false123

If the splicing result calls intern () method, the return value is in the constant pool

String a = "a";
String b = "b";
String c = "a"+"b";
System.err.println(c==a+b); //输出false,证明String类的拼接中只要有一个是变量,结果就存在堆中
String a = "a";
String b = "b";
String c = "a"+"b";
System.err.println(c==(a+b).intern()); //输出true,说明如果拼接结果调用intern()方法，返回值就在常量池中

The above is the detailed content of What are the characteristics of String class in java. For more information, please follow other related articles on the PHP Chinese website!