Java DoubleBuffer asReadOnlyBuffer()方法及示例

java.nio.DoubleBuffer 类的 asReadOnlyBuffer() 方法是用来创建一个新的、只读的双缓冲区，其内容是这个缓冲区的。新的缓冲区是这个缓冲区的复制品。因此，对这个缓冲区的内容所做的改变将在新的缓冲区中可见。

由于新的缓冲区是只读的，因此不允许对其内容进行任何修改。两个缓冲区的位置、极限和标记值将是独立的。新缓冲区的容量、极限、位置和标记值将与这个缓冲区的相同。如果这个缓冲区本身是只读的，那么这个方法的行为与复制方法完全相同。

语法

public abstract DoubleBuffer asReadOnlyBuffer()

返回值： 该方法返回 新的、只读的双缓冲区 ，其内容与该缓冲区的内容相同。

下面是说明asReadOnlyBuffer()方法的例子。

例1 :

// Java program to demonstrate// asReadOnlyBuffer() method  import java.nio.*;import java.util.*;  public class GFG {      public static void main(String[] args)    {          // Declaring the capacity of the DoubleBuffer        int capacity = 10;          // Creating the DoubleBuffer        try {              // creating object of floatbuffer            // and allocating size capacity            DoubleBuffer db = DoubleBuffer.allocate(capacity);              // putting the value in floatbuffer            db.put(8.56);            db.put(2, 9.61);            db.rewind();              // print the DoubleBuffer            System.out.println("Original DoubleBuffer: "                               + Arrays.toString(db.array()));              // Creating a read-only copy of DoubleBuffer            // using asReadOnlyBuffer() method            DoubleBuffer floatBuffer = db.asReadOnlyBuffer();              // print the DoubleBuffer            System.out.print("\nReadOnlyBuffer DoubleBuffer: ");              while (floatBuffer.hasRemaining())                System.out.print(floatBuffer.get() + ", ");        }          catch (IllegalArgumentException e) {              System.out.println("IllegalArgumentException catched");        }          catch (ReadOnlyBufferException e) {              System.out.println("ReadOnlyBufferException catched");        }    }}

输出:

Original DoubleBuffer: [8.56, 0.0, 9.61, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]ReadOnlyBuffer DoubleBuffer: 8.56, 0.0, 9.61, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0,

例2 :

// Java program to demonstrate// asReadOnlyBuffer() method  import java.nio.*;import java.util.*;  public class GFG {      public static void main(String[] args) throws Exception    {          // Declaring the capacity of the db        int capacity1 = 10;          // Declaring the capacity of the db1        int capacity2 = 5;          // Creating the DoubleBuffer        try {              //            // db            //            // creating object of Doublebuffer db            // and allocating size capacity            DoubleBuffer db = DoubleBuffer.allocate(capacity1);              // putting the value in db            db.put(8.56);            db.put(2, 9.61);            db.rewind();              // print the DoubleBuffer            System.out.println("DoubleBuffer db: "                               + Arrays.toString(db.array()));              //            // db1            //            // creating object of Doublebuffer db1            // and allocating size capacity            DoubleBuffer db1 = DoubleBuffer.allocate(capacity2);              // putting the value in db1            db1.put(1, 4.56);            db1.put(2, 6.45);            db1.rewind();              // print the DoubleBuffer            System.out.println("\nDoubleBuffer db1: "                               + Arrays.toString(db1.array()));              // Creating a read-only copy of DoubleBuffer            // using asReadOnlyBuffer() method            DoubleBuffer readOnlyDb = db.asReadOnlyBuffer();              // print the DoubleBuffer            System.out.print("\nReadOnlyBuffer DoubleBuffer: ");              while (readOnlyDb.hasRemaining())                System.out.print(readOnlyDb.get() + ", ");              // try to change readOnlyDb            System.out.println("\n\nTrying to get the array"                               + " from ReadOnlyDb for editing");            Arrays.toString(readOnlyDb.array());        }        catch (IllegalArgumentException e) {            System.out.println("IllegalArgumentException catched");        }        catch (ReadOnlyBufferException e) {            System.out.println("Exception thrown: " + e);        }    }}

输出:

DoubleBuffer db: [8.56, 0.0, 9.61, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]DoubleBuffer db1: [0.0, 4.56, 6.45, 0.0, 0.0]ReadOnlyBuffer DoubleBuffer: 8.56, 0.0, 9.61, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, Trying to get the array from ReadOnlyDb for editingException thrown: java.nio.ReadOnlyBufferException