Java determines whether a string contains characters

java determines whether a string contains characters

3 ways to determine whether a string contains a certain substring (Recommended tutorial: java tutorial)

1. startsWith()

This method has two variants and tests if a string starts at the specified index at the specified prefix or by default at the starting position of the string

The syntax defined for this method is as follows:

public boolean startsWith(String prefix, int toffset)
or
public boolean startsWith(String prefix)

prefix – The prefix to match. Here are the details of the parameters: toffset – where to start looking for the string.

The return value is true and false

import java.io.*;
 
public class Test{
   public static void main(String args[]){
      String Str = new String("Welcome to Yiibai.com");
 
      System.out.print("Return Value :" );
      System.out.println(Str.startsWith("Welcome") );
 
      System.out.print("Return Value :" );
      System.out.println(Str.startsWith("Tutorials") );
 
      System.out.print("Return Value :" );
      System.out.println(Str.startsWith("Yiibai", 11) );
   }
}

2. contains method

java.lang.String.contains()

The method returns true if and only if this string contains the specified Char value sequence

The return value is true and false

public static void main(String[] args) {
        String str = "abc";
        boolean status = str.contains("a");
        if(status){
            System.out.println("包含");
        }else{
            System.out.println("不包含");
        }
    }

3. IndexOf method

The purpose of java.lang.String.indexOf() is Find the position of a word in a string, and also determine whether a string contains a certain character.

The return value of indexOf is int

public static void main(String[] args) {
    String str1 = "abcdefg";
    int result1 = str1.indexOf("ab");
    if(result1 != -1){
        System.out.println("字符串str中包含子串“ab”"+result1);
    }else{
        System.out.println("字符串str中不包含子串“ab”"+result1);
    }
}

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