Java中的 RuleBasedCollator compare() 方法与示例

Java.text.RuleBasedCollator类的compare()方法用于比较两个对象的强度，它会根据结果返回 0，正负值作为输出。

句法：

public int compare(Object o1, Object o2)

参数：此方法采用两个将要进行比较的对象。
返回值：如果第一个对象等于、大于或小于另一个对象，则它将分别返回零、正和负值。
异常：如果参数之一为空，此方法将抛出NullPointerException 。

以下是说明compare()方法的示例：

示例 1：

Java

// 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() method
            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

示例 2：

Java

// 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() method
            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

参考： https://docs.oracle.com/javase/9/docs/api/ Java/text/RuleBasedCollator.html#compare-java.lang.String-java.lang.String-