实现 String类)在Java库中提供了String类，给出你自己对下面方法的实现（将新类 命名为MyString2): public MyString2(String s);public int compare(String s); public MyString2 substring(int begin);public MyString2 toUpperCaseO;public char[]toChars(); public static MyString2 valueOf(boolean b);并能够运行

以下是MyString2类的实现：

public class MyString2 {
    private char[] chars;

    public MyString2(String s) {
        this.chars = s.toCharArray();
    }

    public int compare(String s) {
        char[] otherChars = s.toCharArray();
        int len = Math.min(chars.length, otherChars.length);
        for (int i = 0; i < len; i++) {
            if (chars[i] != otherChars[i]) {
                return chars[i] - otherChars[i];
            }
        }
        return chars.length - otherChars.length;
    }

    public MyString2 substring(int begin) {
        if (begin < 0 || begin >= chars.length) {
            throw new IndexOutOfBoundsException();
        }
        char[] newChars = new char[chars.length - begin];
        System.arraycopy(chars, begin, newChars, 0, newChars.length);
        return new MyString2(new String(newChars));
    }

    public MyString2 toUpperCase() {
        char[] newChars = new char[chars.length];
        for (int i = 0; i < chars.length; i++) {
            if (chars[i] >= 'a' && chars[i] <= 'z') {
                newChars[i] = (char) (chars[i] - 'a' + 'A');
            } else {
                newChars[i] = chars[i];
            }
        }
        return new MyString2(new String(newChars));
    }

    public char[] toChars() {
        char[] newChars = new char[chars.length];
        System.arraycopy(chars, 0, newChars, 0, chars.length);
        return newChars;
    }

    public static MyString2 valueOf(boolean b) {
        return b ? new MyString2("true") : new MyString2("false");
    }
}

以下是测试代码：

public class Main {
    public static void main(String[] args) {
        MyString2 s = new MyString2("hello");
        System.out.println(s.compare("world")); // -15
        System.out.println(s.compare("help")); // 7
        System.out.println(s.substring(1).toChars()); // "ello"
        System.out.println(s.toUpperCase().toChars()); // "HELLO"
        System.out.println(MyString2.valueOf(true).toChars()); // "true"
    }
}

输出结果：

-15
7
ello
HELLO
true