Java Double.compareTo()方法及示例

java.lang.Double.compareTo() 是java中的一个内置方法，可以对两个Double对象进行数字比较。如果该对象等于参数对象，该方法返回0；如果该对象在数字上小于参数对象，则返回小于0；如果该对象在数字上大于参数对象，则返回大于0的值。

语法

public int compareTo(Object obj)

参数： 该方法接受一个参数。

obj – 被比较的对象。

返回值： 该函数可以返回三个值。

等于0：对象等于参数对象
小于0：对象小于参数对象
大于0：对象大于参数对象。

下面的程序说明了java.lang.Double.compareTo()方法的工作。

程序1： 当两个对象都不同时。

// Java program to demonstrate
// of java.lang.Double.compareTo() method
import java.lang.Math;
  
class Gfg1 {
  
    // Driver code
    public static void main(String args[])
    {
  
        // When two objects are different
        Double obj1 = new Double(124);
        Double obj2 = new Double(167);
        int compareValue = obj1.compareTo(obj2);
  
        if (compareValue == 0)
            System.out.println("object1 and object2 are equal");
        else if (compareValue < 0)
            System.out.println("object1 is less than object2");
        else
            System.out.println("object1 is greater than object2");
    }
}

输出。

object1 is less than object2

程序2： 当没有传递参数时。

// Java program to demonstrate
// of java.lang.Double.compareTo() method
import java.lang.Math;
  
class Gfg1 {
  
    // Driver code
    public static void main(String args[])
    {
        // When no argument is passed
        Double obj1 = new Double(124);
        Double obj2 = new Double(167);
  
        int compareValue = obj1.compareTo();
  
        if (compareValue == 0)
            System.out.println("object1 and object2 are equal");
        else if (compareValue < 0)
            System.out.println("object1 is less than object2");
        else
            System.out.println("object1 is greater than object2");
    }
}

输出

prog.java:14: error: method compareTo in class Double 
cannot be applied to given types;
        int compareValue = obj1.compareTo();
                               ^
  required: Double
  found: no arguments
  reason: actual and formal argument lists differ in length
1 error

程序3： 当对象以外的任何东西作为参数被传递时。

// Java program to demonstrate
// of java.lang.Double.compareTo() method
import java.lang.Math;
  
class Gfg1 {
  
    // Driver code
    public static void main(String args[])
    {
  
        // When anything other than object
        // argument is passed
        Double obj1 = new Double(124);
  
        int compareValue = obj1.compareTo("gfg");
  
        if (compareValue == 0)
            System.out.println("object1 and object2 are equal");
        else if (compareValue < 0)
            System.out.println("object1 is less than object2");
        else
            System.out.println("object1 is greater than object2");
    }
}

输出。

prog.java:15: error: incompatible types: String cannot be converted to Double
        int compareValue = obj1.compareTo("gfg");
                                          ^
Note: Some messages have been simplified; recompile with 
-Xdiags:verbose to get full output
1 error