How does the compareTo method in Java sort?

In Java, the compareTo() method is used for comparing and sorting data. It is a method defined in the Comparable interface, which needs to be implemented in a class in order to use it.

The return type of the compareTo() method is int, the specific rules for its return value are as follows:

1. Return a negative integer if the invoking object is smaller than the parameter object.
2. Return 0 if the calling object is equal to the parameter object.
3. If the calling object is greater than the parameter object, a positive integer is returned.

The compareTo() method can implement different sorting methods as needed by comparing the properties or values of objects. For example, for sorting integer objects, the following method can be used:

public class Integer implements Comparable<Integer> {
    private int value;

    // 构造方法和其他方法省略

    @Override
    public int compareTo(Integer other) {
        return this.value - other.value;
    }
}

In this example, the compareTo() method compares the values of two integer objects. If the value of the calling object is less than the value of the parameter object, it returns a negative integer. If the values of the two objects are equal, it returns 0. If the value of the calling object is greater than the value of the parameter object, it returns a positive integer.

By implementing the Comparable interface and the compareTo() method, we can use sorting methods in the Java standard library, such as Collections.sort(), to sort objects.