更改方法中的变量值,Java

public class Main {
    public static void main(String[] args) {
        int x = 10;
        x = changeValue(x);
        System.out.println(x); // 输出 20
    }

    public static int changeValue(int value) {
        value = value * 2;
        return value;
    }
}

public class Main {
    public static void main(String[] args) {
        int x = 10;
        changeValue(x);
        System.out.println(x); // 输出 20
    }

    public static void changeValue(int value) {
        value = value * 2;
    }
}

public class Main {
    public static void main(String[] args) {
        int[] x = {10};
        changeValue(x);
        System.out.println(x[0]); // 输出 20
    }

    public static void changeValue(int[] value) {
        value[0] = value[0] * 2;
    }
}

public class Main {
    public static void main(String[] args) {
        CustomObject x = new CustomObject(10);
        changeValue(x);
        System.out.println(x.getValue()); // 输出 20
    }

    public static void changeValue(CustomObject value) {
        value.setValue(value.getValue() * 2);
    }
}

class CustomObject {
    private int value;

    public CustomObject(int value) {
        this.value = value;
    }

    public int getValue() {
        return value;
    }

    public void setValue(int value) {
        this.value = value;
    }
}