Java Console readPassword()用法及代碼示例

Java中的Console類的readPassword()方法有兩種類型：

1. Java中Console類的readPassword()方法用於在禁用了回顯的情況下從控製台讀取密碼或密碼。

用法:

public char[] readPassword()

參數：此方法不接受任何參數。

返回值：此方法返回一個字符數組，其中包含從控製台讀取的密碼或口令。如果流結束，則返回null。

異常：如果發生I /O錯誤，則此方法將引發IOError。

注意：System.console()在在線IDE中返回null。

以下示例程序旨在說明IO包中Console類中的readPassword()方法：

程序1:

// Java program to illustrate 
// Console readPassword() method 
  
import java.io.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
        // Create the console object 
        Console cnsl 
            = System.console(); 
  
        if (cnsl == null) { 
            System.out.println( 
                "No console available"); 
            return; 
        } 
  
        // Read line 
        String str = cnsl.readLine( 
            "Enter username:"); 
  
        // Print username 
        System.out.println( 
            "Username:" + str); 
  
        // Read password 
        // into character array 
        char[] ch = cnsl.readPassword( 
            "Enter password:"); 
  
        // Print password 
        System.out.println( 
            "Password:" + ch); 
    } 
}

輸出：

程序2:

// Java program to illustrate 
// Console readPassword() method 
  
import java.io.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
        // Create the console object 
        Console cnsl 
            = System.console(); 
  
        if (cnsl == null) { 
            System.out.println( 
                "No console available"); 
            return; 
        } 
  
        // Read line 
        String str = cnsl.readLine( 
            "Enter username:"); 
  
        // Print username 
        System.out.println( 
            "Username:" + str); 
  
        // Read password 
        // into character array 
        char[] ch = cnsl.readPassword( 
            "Enter password:"); 
  
        // Print password 
        System.out.println( 
            "Password:" + ch); 
    } 
}

輸出：

2. Java中Console類的readPassword(String，Object)方法用於通過提供格式化的提示從控製台讀取密碼或密碼。它返回字符數組中的密碼。

用法:

public char[] readPassword(String fmt,
                      Object... args)

參數：此方法接受兩個參數：

fmt-它表示字符串的格式。
args-它表示由字符串格式的格式說明符引用的參數。

返回值：此方法返回包含從控製台讀取的密碼或密碼短語的字符數組。如果流結束，則返回null。

異常：

IllegalFormatException-如果字符串格式包含非法語法，或者格式說明符與給定參數不兼容，或者給定格式字符串或其他非法條件，則此方法將引發IllegalFormatException。
IOError-如果發生I /O錯誤，則此方法將引發IOError。

以下示例程序旨在說明IO包中Console類中的readPassword(String，Object)方法：

程序1:

// Java program to illustrate 
// Console readPassword(String, Object) method 
  
import java.io.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
        // Create the console object 
        Console cnsl 
            = System.console(); 
  
        if (cnsl == null) { 
            System.out.println( 
                "No console available"); 
            return; 
        } 
  
        String fmt = "%2$5s %3$10s%n"; 
  
        // Read line 
        String un = cnsl.readLine( 
            fmt, "Enter", "Username:"); 
  
        // Print username 
        System.out.println( 
            "Username:" + un); 
  
        // Read password 
        // into character array 
        char[] pwd = cnsl.readPassword( 
            fmt, "Enter", "Password:"); 
  
        // Print password 
        System.out.println( 
            "Password:" + pwd); 
    } 
}

輸出：

程序2:

// Java program to illustrate 
// Console readPassword(String, Object) method 
  
import java.io.*; 
  
public class GFG { 
    public static void main(String[] args) 
    { 
        // Create the console object 
        Console cnsl 
            = System.console(); 
  
        if (cnsl == null) { 
            System.out.println( 
                "No console available"); 
            return; 
        } 
  
        String fmt = "%2$5s %3$10s%n"; 
  
        // Read line 
        String un = cnsl.readLine( 
            fmt, "Enter", "Username:"); 
  
        // Print username 
        System.out.println( 
            "Username:" + un); 
  
        // Read password 
        // into character array 
        char[] pwd = cnsl.readPassword( 
            fmt, "Enter", "Password:"); 
  
        // Print password 
        System.out.println( 
            "Password:" + pwd); 
    } 
}

輸出：

參考文獻：
1. https://docs.oracle.com/javase/10/docs/api/java/io/Console.html#readPassword()
2. https://docs.oracle.com/javase/10/docs/api/java/io/Console.html#readPassword(java.lang.String, java.lang.Object…)

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