Java Java.lang.String.copyValueOf()用法及代碼示例

copyValueOf()主要將字符數組的內容複製到字符串中。可以使用此函數的兩個變體，並且本文都會對此進行討論。實施1：

用法:
public static String copyValueOf(char[] ch)
參數:
ch:The character array.
返回值:
This function returns the string with the contents of character array copied

// Java code to demonstrate the working of  
// copyValueOf implementation 1  
public class Copy1 { 
  public static void main(String args[]) { 
        
    // Initialising Character array 
     char[] ch = {'A', 's', 't', 'h', 'a', ' ', 'T', 'y', 'a', 'g', 'i'}; 
       
     // Initialising String 
     String ch2 = ""; 
       
     // Copying value in ch2 
     // now ch2 is equal to "Astha Tyagi" 
     ch2 = ch2.copyValueOf( ch ); 
       
     // Printing String 
     System.out.println("The new copied string is:" + ch2); 
  } 
}

輸出：

The new copied string is:Astha Tyagi

在第二種實現中，也可以提取子數組而不是整個數組。
實施2：

用法:
public static String copyValueOf(char[] ch, int index, int num)
參數:
ch:The character array.
index:  The starting position of array from which copy is to start.
num: Number of elements that has to be copied. 
返回值:
This function returns the string with the contents of character array copied

// Java code to demonstrate the working of  
// copyValueOf implementation 2 
public class Copy2 { 
  public static void main(String args[]) { 
        
    // Initialising Character array 
     char[] ch = {'A', 's', 't', 'h', 'a', ' ', 'T', 'y', 'a', 'g', 'i'}; 
       
     // Initialising String 
     String ch2 = ""; 
       
     // Copying value in ch2 
     // only first 5 are extracted 
     // now ch2 is equal to "Astha" 
     ch2 = ch2.copyValueOf( ch , 0, 5 ); 
       
     // Printing String 
     System.out.println("The new copied string is:" + ch2); 
  } 
}

輸出：

The new copied string is:Astha

可能的應用：該函數可用於使用實現2從字符串中僅複製或提取前綴或後綴。一個可能的示例可以是僅從處理名稱的給定“ Rs 1000”類型的字符串中提取數量。

// Java code to demonstrate the application of  
// copyValueOf  
public class Appli2 { 
  public static void main(String args[]) { 
        
    // Initialising Character array 
     char[] ch = {'R', 's', ' ', '1', '0', '2', '4' }; 
       
     // Original array 
     System.out.print("The original array is:"); 
     for (int i=0; i< ch.length ; i++)  
     System.out.print(ch[i]); 
       
      System.out.print("\n"); 
       
     // Initialising String 
     String ch2 = ""; 
       
     // Copying value in ch2 
     // Rs is not included 
     // now ch2 is equal to "1024" 
     ch2 = ch2.copyValueOf( ch , 3, 4 ); 
       
     // Printing String 
     System.out.println("The new string is:" + ch2); 
  } 
}

輸出：

The original array is:Rs 1024
The new string is:1024

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