stringcompare.java

金旭亮的java教案

//  StringCompare
// This program demonstrates the methods equals, 
// equalsIgnoreCase, compareTo, and regionMatches 
// of the String class.
import javax.swing.JOptionPane;

public class StringCompare {
   public static void main( String args[] )
   {
      String s1, s2, s3, s4, output;

      s1 = new String( "hello" );
      s2 = new String( "good bye" );
      s3 = new String( "Happy Birthday" );
      s4 = new String( "happy birthday" );

      output = "s1 = " + s1 + "\ns2 = " + s2 +
               "\ns3 = " + s3 + "\ns4 = " + s4 + "\n\n";

      //test for equality
      //equals用于比较两对象的内容是否相等.
      //自定义对象时需要重载此方法
      if ( s1.equals( "hello" ) )
         output += "s1 equals \"hello\"\n";
      else
         output += "s1 does not equal \"hello\"\n"; 

      // test for equality with ==
      //比对引用.只有两个引用指向同一个对象,则结果为true
      if ( s1 == "hello" )
         output += "s1 == \"hello\"\n";
      else
         output += "s1 does not == \"hello\"\n";

      // test for equality--ignore case
      if ( s3.equalsIgnoreCase( s4 ) )
         output += "s3 equals s4\n";
      else
         output += "s3 does not equal s4\n";

      // test compareTo
      //使用字典法进行比较,返回0表两字串相等,小于返回负值,大于返回正值

      output +=
         "\ns1.compareTo( s2 ) is " + s1.compareTo( s2 ) +
         "\ns2.compareTo( s1 ) is " + s2.compareTo( s1 ) +
         "\ns1.compareTo( s1 ) is " + s1.compareTo( s1 ) +
         "\ns3.compareTo( s4 ) is " + s3.compareTo( s4 ) +
         "\ns4.compareTo( s3 ) is " + s4.compareTo( s3 ) +
         "\n\n";

      // test regionMatches (case sensitive)
      //比较两字串中的某一部分是否相等
      //参数含义如下:
      //1.调用这个方法的字串中的起始下标
      //2.要比较的字串
      //3.要比较的字串的起始下标
      //4.要比较的字串比较的字符长度
      if ( s3.regionMatches( 0, s4, 0, 5 ) )
         output += "First 5 characters of s3 and s4 match\n";
      else
         output +=
            "First 5 characters of s3 and s4 do not match\n";

      // test regionMatches (ignore case)
      
      if ( s3.regionMatches( true, 0, s4, 0, 5 ) )
         output += "First 5 characters of s3 and s4 match";
      else
         output +=
            "First 5 characters of s3 and s4 do not match";

      JOptionPane.showMessageDialog( null, output,
         "Demonstrating String Class Constructors",
         JOptionPane.INFORMATION_MESSAGE );

      System.exit( 0 );
   }
}

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 * (C) Copyright 1999 by Deitel & Associates, Inc. and Prentice Hall.     *
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