Java中String类startsWith方法详解

public class StartsWithExample {
    public static void main(String[] args) {
        String str = "hello world";

        // 使用 startsWith 检查字符串是否以 "hel" 开始
        boolean startsWithHel = str.startsWith("hel");
        System.out.println("Does the string start with 'hel'? " + startsWithHel); // 输出 true

        // 使用 startsWith 检查字符串是否以 "world" 开始
        boolean startsWithWorld = str.startsWith("world");
        System.out.println("Does the string start with 'world'? " + startsWithWorld); // 输出 false

        // 使用 startsWith 检查从索引 6 开始的子字符串是否以 "world" 开始
        boolean startsAt6WithWorld = str.startsWith("world", 6);
        System.out.println("Does the string start at index 6 with 'world'? " + startsAt6WithWorld); // 输出 true
    }
}

public class StartsWithDemo {
    public static void main(String[] args) {
        String str1 = "Java Programming";
        String str2 = "Java";
        String str3 = "Programming";
        String str4 = "java";

        // 检查 str1 是否以 "Java" 开始
        System.out.println(str1.startsWith("Java")); // 输出 true

        // 检查 str1 是否以 "Java" 开始，忽略大小写
        System.out.println(str1.toLowerCase().startsWith(str4.toLowerCase())); // 输出 true

        // 检查 str1 是否以 "Prog" 开始，从第 5 个字符开始（索引为 4）
        System.out.println(str1.startsWith("Prog", 5)); // 输出 true

        // 检查 str1 是否以空字符串开头
        System.out.println(str1.startsWith("")); // 输出 true

        // 使用循环来检查数组中的每个字符串是否以特定字符串开头
        String[] words = {"start", "startle", "stardust", "starship", "station"};
        String prefix = "star";
        for (String word : words) {
            if (word.startsWith(prefix)) {
                System.out.println(word + " starts with " + prefix);
            } else {
                System.out.println(word + " does not start with " + prefix);
            }
        }
        // 输出:
        // start does not start with star
        // startle starts with star
        // stardust starts with star
        // starship starts with star
        // station does not start with star

        // 在实际应用中，比如文件路径检查
        String filePath = "/home/user/documents/report.txt";
        // 检查是否在某个特定目录下
        if (filePath.startsWith("/home/user/")) {
            System.out.println("The file is in the user's home directory.");
        } else {
            System.out.println("The file is not in the user's home directory.");
        }
        // 输出: The file is in the user's home directory.
    }
}

 public class StartsWithExample {    
	 public static void main(String[] args) {
		         String str = "abcHello, World!";                
		         // 从索引3开始检查是否以"Hello"为前缀        
		         boolean isHelloPrefixFromIndex3 = str.startsWith("Hello", 3);        
		         System.out.println("Does '" + str + "' start with 'Hello' from index 3? " + isHelloPrefixFromIndex3); // 输出: true    
	         }
}