Java Deflater setLevel()用法及代碼示例

java.util.zip中Deflater類的setLevel()函數將當前壓縮級別設置為指定值。壓縮級別是從0到9的整數值。函數簽名：

public void setLevel(int level)

用法:

d.setLevel(int);

參數：該函數需要一個整數值，該整數值是指定的壓縮值

返回類型：該函數不返回任何值。

異常：如果壓縮級別無效，該函數將拋出IllegalArgumentException。

放氣水平的一些恒定值：

BEST_COMPRESSION：壓縮級別以獲得最佳壓縮
BEST_SPEED：壓縮級別，可實現最快的壓縮。
DEFAULT_COMPRESSION：默認壓縮級別。
NO_COMPRESSION：無壓縮的壓縮級別。

範例1：

// Java program to describe the use 
// of setLevel() function 
  
import java.util.zip.*; 
import java.io.UnsupportedEncodingException; 
  
class GFG { 
  
    // Function to compress the string to the given level 
    static void compression(int level, String text) 
        throws UnsupportedEncodingException 
    { 
        // deflater 
        Deflater d = new Deflater(level); 
  
        // set the Input for deflator 
        d.setInput(text.getBytes("UTF-8")); 
  
        // finish 
        d.finish(); 
  
        // output bytes 
        byte output[] = new byte[1024]; 
  
        // compress the data 
        int size = d.deflate(output); 
  
        // compressed String 
        System.out.println("Compressed String with level ="
                           + level + ":"
                           + new String(output) 
                           + "\n Size " + size); 
  
        d.end(); 
    } 
  
    // Driver code 
    public static void main(String args[]) 
        throws UnsupportedEncodingException 
    { 
  
        // get the text 
        String pattern = "GeeksforGeeks", text = ""; 
  
        // generate the text 
        for (int i = 0; i < 4; i++) 
            text += pattern; 
  
        // original String 
        System.out.println("Original String:" + text 
                           + "\n Size " + text.length()); 
  
        // default 
        compression(Deflater.DEFAULT_COMPRESSION, text); 
  
        // no compression 
        compression(Deflater.NO_COMPRESSION, text); 
  
        // Best compression 
        compression(Deflater.BEST_COMPRESSION, text); 
  
        // Best Speed 
        compression(Deflater.BEST_SPEED, text); 
    } 
}

輸出：

Original String:GeeksforGeeksGeeksforGeeksGeeksforGeeksGeeksforGeeks
 Size 52
Compressed String with level =-1:x?sOM?.N?/r???q??
 Size 21
Compressed String with level =0:x4??GeeksforGeeksGeeksforGeeksGeeksforGeeksGeeksforGeeks??
 Size 63
Compressed String with level =9:x?sOM?.N?/r???q??
 Size 21
Compressed String with level =1:xsOM?.N?/r?`?0??
 Size 22

參考： https://docs.oracle.com/javase/7/docs/api/java/util/zip/Deflater.html#setLevel()

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