【JAVASE】带你了解String类的常用方法和常见操作

public class StringMethodsExample {
    public static void main(String[] args) {
        String str = "Hello, World!";
 
        // 获取长度
        int length = str.length();
        System.out.println("Length: " + length); // 输出: Length: 13
 
        // 获取字符
        char charAt = str.charAt(6);
        System.out.println("Character at index 6: " + charAt); // 输出: Character at index 6: W
 
        // 查找字符串
        int index = str.indexOf("World");
        System.out.println("Index of 'World': " + index); // 输出: Index of 'World': 7
 
        // 查找字符
        int indexOfChar = str.indexOf('W');
        System.out.println("Index of 'W': " + indexOfChar); // 输出: Index of 'W': 6
 
        // 替换字符串
        String replaced = str.replace("World", "Java");
        System.out.println("Replaced string: " + replaced); // 输出: Replaced string: Hello, Java!
 
        // 分割字符串
        String[] split = str.split(", ");
        System.out.println("Split string: " + Arrays.toString(split)); // 输出: Split string: [Hello, World!]
 
        // 子字符串
        String substring = str.substring(0, 5);
        System.out.println("Substring: " + substring); // 输出: Substring: Hello
 
        // 转换为大写
        String toUpperCase = str.toUpperCase();
        System.out.println("Upper case string: " + toUpperCase); // 输出: Upper case string: HELLO, WORLD!
 
        // 转换为小写
        String toLowerCase = str.toLowerCase();
        System.out.println("Lower case string: " + toLowerCase); // 输出: Lower case string: hello, world!
 
        // 判断字符串是否相等
        boolean isEqual = str.equals("Hello, World!");
        System.out.println("Is equal to 'Hello, World!': " + isEqual); // 输出: Is equal to 'Hello, World!': true
 
        // 判断字符串是否以特定子串开始
        boolean startsWith = str.startsWith("Hello");
        System.out.println("Starts with 'Hello': " + startsWith); // 输出: Starts with 'Hello': true
 
        // 判断字符串是否以特定子串结束
        boolean endsWith = str.endsWith("World!");
        System.out.println("Ends with 'World!': " + endsWith); // 输出: Ends with 'World!': true
 
        // 判断字符串是否为空
        boolean isEmpty = str.isEmpty();
        System.out.println("Is empty: " + isEmpty); // 输出: Is empty: false
    }
}

这段代码展示了Java中String类的一些常用方法，包括获取长度、获取字符、查找字符串或字符、替换字符串、分割字符串、获取子字符串、转换大小写、判断字符串是否相等以及是否以特定子串开始或结束等。这些方法对于字符串操作是非常基础和重要的。