Java object-oriented basic String class

Java object-oriented basic String class

Two instantiation methods of the String class

A. Direct assignment

 

Public class Stringlei {public static void main (String args []) {String name = "zhangsan"; System. out. println ("name:" + name );}}

B. Use the keyword new

 

 

Public class Stringlei {public static void main (String args []) {String name = new String ("Zhang San"); System. out. println ("name:" + name );}}

String Content Comparison

 

 

1. Use "=" to compare

public class Stringlei{public static void main(String args[]){   String  str1="hello";   String str2=new String("hello");   String str3=str2;   System.out.println("str1==str2?-->"+(str1==str2));//false   System.out.println("str1==str3?-->"+(str1==str3));//false   System.out.println("str2==str3?-->"+(str2==str3));//true}}

We can see that: "=" determines whether the address space is equal to the address space. To determine the content, you must use the equals () method provided in String to complete the process:

 

public class Stringlei{public static void main(String args[]){   String  str1="hello";   String str2=new String("hello");   String str3=str2;   System.out.println("str1==str2?-->"+(str1.equals(str2)));//true   System.out.println("str1==str3?-->"+(str1.equals(str3)));//true   System.out.println("str2==str3?-->"+(str2.equals(str3)));//true}}

Differences between the two instantiation Methods

 

 

You can use the direct value assignment and new call constructor in the String. Compare two methods.

A String is an anonymous String object.

Public class Stringlei {public static void main (String args []) {String str1 = "hello "; // actually, the heap memory space is directed to the stack memory space String str2 = "hello"; String str3 = "hello"; System. out. println ("str1 = str2? --> "+ (Str1 = str2); // true System. out. println (" str1 = str3? --> "+ (Str1 = str3); // true System. out. println (" str2 = str3? --> "+ (Str2 = str3); // true }}

The content of the string cannot be changed.

 

public class Stringlei{public static void main(String args[]){   String  str="hello";   str=str+" world!";   System.out.println("str = " +str);}}

Here, the content in str is not simply changed, for example: