用示例缓冲 Java 中的 clear()方法
原文:https://www . geesforgeks . org/buffer-clear-methods-in-Java-with-examples/
java.nio.ByteBuffer 类的 clear() 方法用于清除该缓冲区。位置设置为零，限制设置为容量，标记被丢弃。在使用一系列通道读取或放置操作来填充此缓冲区之前，请调用此方法。
例如:
buf.clear(); // Prepare buffer for reading
in.read(buf); // Read data
这种方法实际上并不擦除缓冲区中的数据，但它的命名就好像它擦除了数据一样，因为它最常用于这种情况。
语法:
public Buffer clear()
返回值:这个方法返回这个缓冲区。
以下是说明 clear()方法的示例:
示例 1:
// Java program to demonstrate
// clear() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
try {
byte[] barr = { 10, 20, 30, 40 };
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.wrap(barr);
// Typecasting ByteBuffer into Buffer
Buffer bb1 = (Buffer)bb;
// try to set the position at index 2
bb1.position(2);
// Set this buffer mark position
// using mark() method
bb1.mark();
// try to set the position at index 4
bb1.position(4);
// display position
System.out.println("position before reset: "
+ bb1.position());
// try to call clear() to restore
// to the position at index 0
// by discarding the mark
bb1.clear();
// display position
System.out.println("position after reset: "
+ bb1.position());
}
catch (InvalidMarkException e) {
System.out.println("new position is less than "
+ "the position we marked before ");
System.out.println("Exception throws: " + e);
}
}
}
输出:
position before reset: 4
position after reset: 0
示例 2:
// Java program to demonstrate
// clear() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
try {
byte[] barr = { 10, 20, 30, 40 };
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.wrap(barr);
// Typecasting ByteBuffer into Buffer
Buffer bb1 = (Buffer)bb;
// try to set the position at index 2
bb1.position(3);
// display position
System.out.println("position before clear: "
+ bb1.position());
// try to call clear() to restore
// to the position at index 0
// by discarding the mark
bb1.clear();
// display position
System.out.println("position after clear: "
+ bb1.position());
}
catch (InvalidMarkException e) {
System.out.println("new position is less than "
+ "the position we marked before ");
System.out.println("Exception throws: " + e);
}
}
}
输出:
position before clear: 3
position after clear: 0
参考:https://docs . Oracle . com/javase/9/docs/API/Java/nio/buffer . html # clear–
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