Common string operations in java

Java String class Strings are widely used in Java programming. Strings are objects in Java. Java provides the String class to create and operate strings. Today I will introduce to you some common string manipulation methods in Java.

1. Use the length() method to get the length of the string

public class  maintest {
    public static void main(String[] args) {
        String str = "abcdefg";
        //length():统计当前字符串的字符个数
        int i = str.length();
        System.out.println(i);
        }
    }

2. Use the indexOf() method to find the position of the specified character in the string

public class  maintest {
    public static void main(String[] args) {
        String str = "abcdefg";
        //indexOf()：查找指定字符再字符串中的位置
        int index = str.indexOf("a");
        System.out.println(index);
        }
      }

3. Use the toUpperCase() method to change the characters in the string to uppercase

public class  maintest {
    public static void main(String[] args) {
        String str = "abcdefg";
        //小写转大写
        //toUpperCase():将字符串中的字符变为了大写形式
        String str = str.toUpperCase();
        System.out.println(str);
        }
       }

4. Use the toLowerCase() method to change the characters in the string to lowercase

public class  maintest {
    public static void main(String[] args) {
        //toLowerCase():将字符串中的字符变为小写
        String str = "WWMMDDHH";
        String str1 = str3.toLowerCase();
        System.out.println(str);
       }
     }

5. Use the substring() method to intercept the string

public class  maintest {
    public static void main(String[] args) {
        String str = "abcdefg";
        //substring:截取字符串
        String str = "abcdefg";
        String str = str5.substring(0, 3);
        System.out.println(str);
        String str = str5.substring(3);
        System.out.println(str);
      }
    }

6. Use the replaceAll() Method to replace the specified content in the current string

public class  maintest {
    public static void main(String[] args) {
        String str = "abcdefg";
        String str = str5.replaceAll("abc", "xyz");
        System.out.println(str);
       }
     }

7. Use the trim() method to remove the spaces at both ends of the current string

public class  maintest {
    public static void main(String[] args) {
        String str = " abc def ";
        System.out.println(str.length());
        String str1 = str9.trim();
        System.out.println(str);
        System.out.println(str1);
    }
 }

8. String string is equal to splicing

public class  maintest {
    public static void main(String[] args) {
        String str1 = "123";
        String str2 = "100";
        System.out.println(str1+str2);
    }
  }

9. Convert a string into an integer

public class  maintest {
    public static void main(String[] args) {
        String str1 = "123";
        String str2 = "100";
        int num1 = Integer.parseInt(str1);
        int num2 = Integer.parseInt(str2);
        System.out.println(num1+num2);
    }
  }

10. Use charAt ()Find the character at the specified position in the string

public class  maintest {
    public static void main(String[] args) {
        String str1000 = "abcde";
        //charAt:找到指定字符串中位置的字符
        char char = str1000.charAt(2);
        System.out.println(char);
    }
   }

The above is the string operation commonly used in Java that I have summarized for everyone. If you want to know more about java, you can click: java tutorial

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