Java字符串的遍历

1. 使用 for 循环遍历字符串

for循环是最常用的遍历字符串的方法之一，可以通过索引访问字符串的每个字符。

public class ForLoopExample {
    public static void main(String[] args) {
        String str = "Hello, Java!";
        
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            System.out.println("Character at index " + i + ": " + c);
        }
    }
}

输出:

Character at index 0: H
Character at index 1: e
Character at index 2: l
Character at index 3: l
Character at index 4: o
Character at index 5: ,
Character at index 6:  
Character at index 7: J
Character at index 8: a
Character at index 9: v
Character at index 10: a
Character at index 11: !

2. 使用 for-each 循环遍历字符串

for-each循环可以用于遍历字符串中的每个字符，但需要先将字符串转换为字符数组。

public class ForEachLoopExample {
    public static void main(String[] args) {
        String str = "Hello, Java!";
        char[] chars = str.toCharArray();
        
        for (char c : chars) {
            System.out.println("Character: " + c);
        }
    }
}

输出:

Character: H
Character: e
Character: l
Character: l
Character: o
Character: ,
Character:  
Character: J
Character: a
Character: v
Character: a
Character: !

Character: !

3. 使用 while 循环遍历字符串

while循环也可以用于遍历字符串，通过索引访问每个字符。

public class WhileLoopExample {
    public static void main(String[] args) {
        String str = "Hello, Java!";
        int i = 0;
        
        while (i < str.length()) {
            char c = str.charAt(i);
            System.out.println("Character at index " + i + ": " + c);
            i++;
        }
    }
}

输出:

Character at index 0: H
Character at index 1: e
Character at index 2: l
Character at index 3: l
Character at index 4: o
Character at index 5: ,
Character at index 6:  
Character at index 7: J
Character at index 8: a
Character at index 9: v
Character at index 10: a
Character at index 11: !

4. 使用 String 的 toCharArray() 方法

toCharArray()方法将字符串转换为一个字符数组，然后可以使用for-each循环或其他数组遍历方法进行遍历。

public class ToCharArrayExample {
    public static void main(String[] args) {
        String str = "Hello, Java!";
        char[] chars = str.toCharArray();
        
        for (int i = 0; i < chars.length; i++) {
            System.out.println("Character at index " + i + ": " + chars[i]);
        }
    }
}

输出:

Character at index 0: H
Character at index 1: e
Character at index 2: l
Character at index 3: l
Character at index 4: o
Character at index 5: ,
Character at index 6:  
Character at index 7: J
Character at index 8: a
Character at index 9: v
Character at index 10: a
Character at index 11: !

5. 使用 String 的 codePoints() 方法遍历 Unicode 代码点

public class CodePointsExample {
    public static void main(String[] args) {
        String str = "Hello, 世界!";
        
        str.codePoints().forEach(cp -> {
            System.out.println("Code point: " + cp);
            System.out.println("Character: " + new String(Character.toChars(cp)));
        });
    }
}

输出:

Code point: 72
Character: H
Code point: 101
Character: e
Code point: 108
Character: l
Code point: 108
Character: l
Code point: 111
Character: o
Code point: 44
Character: ,
Code point: 32
Character:  
Code point: 19990
Character: 界
Code point: 30028
Character: 世
Code point: 33
Character: !

6. 使用 String 的 codePoints() 方法遍历 Unicode 代码点

public class CodePointsExample {
    public static void main(String[] args) {
        String str = "Hello, 世界!";
        
        str.codePoints().forEach(cp -> {
            System.out.println("Code point: " + cp);
            System.out.println("Character: " + new String(Character.toChars(cp)));
        });
    }
}

输出:

Code point: 72
Character: H