Java 中的 CharBuffer asReadOnlyBuffer()方法
原文:https://www . geesforgeks . org/char buffer-as readonly buffer-in-method-in-Java/
java.nio.CharBuffer 类的 asReadOnlyBuffer() 方法用于用该缓冲区的内容创建一个新的只读字符缓冲区。新缓冲区是该缓冲区的副本。因此，对此缓冲区内容所做的更改将在新缓冲区中可见。
由于新缓冲区是只读的，因此不允许对其内容进行任何修改。两个缓冲器的位置、极限和标记值将是独立的。新缓冲区的容量、限制、位置和标记值将与该缓冲区相同。如果此缓冲区本身是只读的，则此方法的行为方式与复制方法完全相同。
语法:
public abstract CharBuffer asReadOnlyBuffer()
返回值:该方法返回新的只读字符缓冲区，其内容与该缓冲区相同。
下面是说明 asReadOnlyBuffer()方法的示例:
实施例 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 CharBuffer
int capacity = 10;
// Creating the CharBuffer
try {
// creating object of charbuffer
// and allocating size capacity
CharBuffer cb = CharBuffer.allocate(capacity);
// putting the value in charbuffer
cb.put('a');
cb.put(2, 'b');
cb.rewind();
// print the charBuffer
System.out.println("Original CharBuffer: "
+ Arrays.toString(cb.array()));
// Creating a read-only copy of CharBuffer
// using asReadOnlyBuffer() method
CharBuffer charBuffer = cb.asReadOnlyBuffer();
// print the CharBuffer
System.out.print("\nReadOnlyBuffer CharBuffer: ");
while (charBuffer.hasRemaining())
System.out.print(charBuffer.get() + ", ");
}
catch (IllegalArgumentException e) {
System.out.println("IllegalArgumentException catched");
}
catch (ReadOnlyBufferException e) {
System.out.println("ReadOnlyBufferException catched");
}
}
}
Output:
Original CharBuffer: [a, , b, , , , , , , ]
ReadOnlyBuffer CharBuffer: a, , b, , , , , , , ,
实施例 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 cb
int capacity1 = 10;
// Declaring the capacity of the cb1
int capacity2 = 5;
// Creating the CharBuffer
try {
//
// cb
//
// creating object of charbuffer cb
// and allocating size capacity
CharBuffer cb = CharBuffer.allocate(capacity1);
// putting the value in cb
cb.put('a');
cb.put(2, 'b');
cb.rewind();
// print the CharBuffer
System.out.println("CharBuffer cb: "
+ Arrays.toString(cb.array()));
//
// cb1
//
// creating object of charbuffer cb1
// and allocating size capacity
CharBuffer cb1 = CharBuffer.allocate(capacity2);
// putting the value in cb1
cb1.put(1, 'c');
cb1.put(2, 'd');
cb1.rewind();
// print the CharBuffer
System.out.println("\nCharBuffer cb1: "
+ Arrays.toString(cb1.array()));
// Creating a read-only copy of CharBuffer
// using asReadOnlyBuffer() method
CharBuffer readOnlyCb = cb.asReadOnlyBuffer();
// print the CharBuffer
System.out.print("\nReadOnlyBuffer CharBuffer: ");
while (readOnlyCb.hasRemaining())
System.out.print(readOnlyCb.get() + ", ");
// try to change readOnlyCb
System.out.println("\n\nTrying to get the array"
+ " from ReadOnlyCb for editing");
char[] fbarr = readOnlyCb.array();
}
catch (IllegalArgumentException e) {
System.out.println("IllegalArgumentException catched");
}
catch (ReadOnlyBufferException e) {
System.out.println("Exception thrown: " + e);
}
}
}
Output:
CharBuffer cb: [a, , b, , , , , , , ]
CharBuffer cb1: [ , c, d, , ]
ReadOnlyBuffer CharBuffer: a, , b, , , , , , , ,
Trying to get the array from ReadOnlyCb for editing
Exception thrown: java.nio.ReadOnlyBufferException
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