java.text.RuleBasedCollat​​or类的compare()方法用于比较两个对象的强度，并且根据结果将返回0，正值和负值作为输出。

用法:

public int compare(Object o1, Object o2)

参数：此方法需要两个对象之间进行比较。

返回值：如果第一个对象等于，小于或小于另一个对象，则它将分别返回零，正值和负值。

异常：如果参数之一为null，则此方法引发NullPointerException。

下面是说明compare()方法的示例：

范例1：

// Java program to demonstrate

// compare() method

import java.text.*;

import java.util.*;

import java.io.*;

public class GFG {

public static void main(String[] argv)

{

try {

// Creating and initializing

// RuleBasedCollator Object

RuleBasedCollator col

= new RuleBasedCollator("< a< b< c< d");

// Creating an initializing

// object for comparison

Object obj1 = "ab";

// Creating an initializing

// Object for comparison

Object obj2 = "Ab";

// compare both object

// using compare() mehtod

int i

= col.compare((String)obj1,

(String)obj2);

// display result

if (i < 0)

System.out.println("ab is less than Ab");

else if (i > 0)

System.out.println("ab is greater than Ab");

else

System.out.println("ab is equal to Ab");

}

catch (ParseException e) {

System.out.println(e);

}

catch (NullPointerException e) {

System.out.println(e);

}

}

}

输出：

ab is less than Ab

范例2：

// Java program to demonstrate

// compare() method

import java.text.*;

import java.util.*;

import java.io.*;

public class GFG {

public static void main(String[] argv)

{

try {

// Creating and initializing RuleBasedCollator Object

RuleBasedCollator col

= new RuleBasedCollator("< a< b< c< d");

// Creating an initializing

// object for comparison

Object obj1 = null;

// Creating an initializing

// Object for comparison

Object obj2 = "Ab";

// compare both object

// using compare() mehtod

int i

= col.compare((String)obj1, (String)obj2);

// display result

if (i < 0)

System.out.println("ab is less than Ab");

else if (i > 0)

System.out.println("ab is greater than Ab");

else

System.out.println("ab is equal to Ab");

}

catch (ParseException e) {

System.out.println(e);

}

catch (NullPointerException e) {

System.out.println("one of the object is null");

System.out.println(e);

}

}

}

输出：

one of the object is null

java.lang.NullPointerException