Java Character isDefined() 方法

6 Nov 2024 | 3 分钟阅读

Character 类的 isDefined(char ch) 方法通常用于确定该字符是否在 Unicode 中已定义。

当且仅当满足以下两个条件之一（或都为 true）时，该字符在 Unicode 中才被定义：

该字符必须在 UnicodeData 文件中有条目。
该字符的范围必须由 UnicodeData 文件定义。

语法

参数

上述方法只需要一个参数

a.) 需要测试的字符。

返回值

isDefined(char ch) 方法返回一个布尔值，即：如果给定的（或指定的）字符在 Unicode 中具有已定义的含义，则返回 true。否则，返回 false。

示例 1

public class JavaCharacterisDefinedExample1 {
	public static void main(String[] args) {
	      // Create char primitives obj1, obj2 and obj3
	      char obj1;
	      char obj2;
	      char obj3;
	      // Assign the values to obj1, obj2 and obj3.
	      obj1 = '@';
	      obj2 = '*';
	      obj3 = '&';
	      // Create the boolean primitives b1, b2,b3.
	      boolean b1;
	      boolean b2;
	      boolean b3;
	      b1 = Character.isDefined(obj1);
	      b2 = Character.isDefined(obj2);
	      b3 = Character.isDefined(obj3);
	      String str1 = "The meaning for the character " +obj1+ " is defined as:  " +b1;
	      String str2 = "The meaning for the character " +obj2+ " is defined as:  " +b2;
	      String str3 = "The meaning for the character " +obj3+ " is defined as:   " +b3;
	      // print b value
	      System.out.println( str1 );
	      System.out.println( str2 );
	      System.out.println( str3 );
	   }
	}

输出

The meaning for the character @ is defined as:  true
The meaning for the character * is defined as:  true
The meaning for the character & is defined as:  true

示例 2

import java.util.Scanner;
public class JavaCharacterisDefinedExample2 {
public static void main(String[] args) {
     // Ask the user to enter the first character.
	System.out.print("Enter a character:   ");		
    // Use scanner to get the user input
	Scanner obj1 = new Scanner(System.in);
   // get a single character
	char value1 = obj1.nextLine().toCharArray()[0];
		
    // Check whether the user input is defined the Unicode or not.
	boolean check1 = Character.isDefined(value1);
   // Print the result
	if(check1){
System.out.print("The user input \'"+value1+"\' is defined in the Unicode\n");
		}
	else{
System.out.print("The user input \'"+value1+"\' is not defined in the Unicode\n");
		}
   // Ask the user to enter the second character.
System.out.print("Enter the second character:   ");				
  // Use scanner to get the user input
    Scanner obj2 = new Scanner(System.in);
  // get a single character
    char value2 = obj2.nextLine().toCharArray()[0];			
  // Check whether the user input is defined the Unicode or not. 
    boolean check2 = Character.isDefined(value2);
  // Print the result
     if(check2){
System.out.print("The user input \'"+value2+"\' is defined in the Unicode");
	   }
     else{
System.out.print("The user input \'"+value2+"\' is not defined in the Unicode");
		}		
       }
}

输出

Enter a character:   $
The user input '$' is defined in the Unicode
Enter the second character:   )
The user input ')' is defined in the Unicode

示例 3

public class JavaCharacterisDefinedExample3 {
	public static void main(String args[])
	  {
	   char ch1 = '1';
	   char ch2 = '2';    
	   char ch3 = '3';    
	   char ch4 = '4';    
	   char ch5 = '5';   
	   boolean b1 = Character.isDefined(ch1);
	   boolean b2 = Character.isDefined(ch2);
	   boolean b3 = Character.isDefined(ch3);
	   boolean b4 = Character.isDefined(ch4);
	   boolean b5 = Character.isDefined(ch5);
System.out.println(ch1 + " is defined in the Unicode character set: " + b1);              
System.out.println(ch2 + " is defined in the Unicode character set: " + b2);  
System.out.println(ch3 + " is defined in the Unicode character set: " + b3);  
System.out.println(ch4 + " is defined in the Unicode character set: " + b4);   
System.out.println(ch5 + " is defined in the Unicode character set: " + b5); 
     	}
}

输出

1 is defined in the Unicode character set: true
2 is defined in the Unicode character set: true
3 is defined in the Unicode character set: true
4 is defined in the Unicode character set: true
5 is defined in the Unicode character set: true

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Java Character isDefined() 方法

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Java Character isDefined() 方法

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示例 1

示例 2

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