Java中的 ByteBuffer getDouble() 方法及示例
getDouble()
Java.nio.ByteBuffer类的getDouble()方法用于读取该缓冲区当前位置接下来的8 个字节，按照当前字节顺序将它们组合成一个double 值，然后将该位置加8。
句法：
public abstract double getDouble()返回值：此方法返回缓冲区当前位置的双精度值
抛出：如果缓冲区的当前位置不小于其限制，则此方法抛出BufferUnderflowException ，然后抛出此异常。
以下是说明 getDouble() 方法的示例：
示例 1：
// Java program to demonstrate
// getDouble() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the ByteBuffer
int capacity = 16;
// Creating the ByteBuffer
try {
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(capacity);
// putting the double value in the bytebuffer
bb.asDoubleBuffer()
.put(1234.3456)
.put(2884.4444);
// rewind the Bytebuffer
bb.rewind();
// print the ByteBuffer
System.out.println("Original ByteBuffer: ");
for (int i = 1; i <= capacity / 8; i++)
System.out.print(bb.getDouble() + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the double at this buffer's current position
// using getDouble() method
double value = bb.getDouble();
// print the char value
System.out.println("\n\nByte Value: " + value);
// Reads the char at this buffer's next position
// using getDouble() method
double value1 = bb.getDouble();
// print the char value
System.out.print("\nNext Byte Value: " + value1);
}
catch (BufferUnderflowException e) {
System.out.println("\nException Thrown : " + e);
}
}
}
输出：
Original ByteBuffer:
1234.3456 2884.4444
Byte Value: 1234.3456
Next Byte Value: 2884.4444
示例 2：
// Java program to demonstrate
// getDouble() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the ByteBuffer
int capacity = 16;
// Creating the ByteBuffer
try {
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(capacity);
// putting the double value in the bytebuffer
bb.asDoubleBuffer()
.put(1234.3456)
.put(2884.4444);
// rewind the Bytebuffer
bb.rewind();
// print the ByteBuffer
System.out.println("Original ByteBuffer: ");
for (int i = 1; i <= capacity / 8; i++)
System.out.print(bb.getDouble() + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the double at this buffer's current position
// using getDouble() method
double value = bb.getDouble();
// print the char value
System.out.println("\n\nByte Value: " + value);
// Reads the char at this buffer's next position
// using getDouble() method
double value1 = bb.getDouble();
// print the char value
System.out.println("\nNext Byte Value: " + value1);
// Reads the char at this buffer's next position
// using getDouble() method
double value2 = bb.getDouble();
}
catch (BufferUnderflowException e) {
System.out.println("\nthere are fewer than "
+ "eight bytes remaining in"
+ " this buffer");
System.out.println("Exception Thrown : " + e);
}
}
}
输出：
Original ByteBuffer:
1234.3456 2884.4444
Byte Value: 1234.3456
Next Byte Value: 2884.4444
there are fewer than eight bytes remaining in this buffer
Exception Thrown : java.nio.BufferUnderflowException
参考： https://docs.oracle.com/javase/9/docs/api/ Java/nio/ByteBuffer.html#getDouble–
getDouble（整数索引）
ByteBuffer的getDouble(int index)方法用于读取给定索引处的八个字节，根据当前字节顺序将它们组合成一个双精度值。
句法 ：
public abstract double getDouble(int index)参数：此方法将索引作为参数，该参数是将从中读取字节的索引。
返回值：此方法返回给定索引处的双精度值
异常：此方法抛出IndexOutOfBoundsException 。如果 index 为负数或不小于缓冲区的限制，则会引发此异常。
以下是说明getDouble(int index)方法的示例：
示例 1：
// Java program to demonstrate
// getDouble() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the ByteBuffer
int capacity = 16;
// Creating the ByteBuffer
try {
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(capacity);
// putting the double value in the bytebuffer
bb.asDoubleBuffer()
.put(1234.3456)
.put(2884.4444);
// rewind the Bytebuffer
bb.rewind();
// Declaring the variable
double c;
// print the ByteBuffer
System.out.println("Original ByteBuffer: ");
for (int i = 1; i <= capacity / 8; i++)
System.out.print(bb.getDouble() + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the double at this buffer's current position
// using getDouble() method
double value = bb.getDouble(0);
// print the char value
System.out.println("\n\nByte Value: " + value);
// Reads the char at this buffer's next position
// using getDouble() method
double value1 = bb.getDouble(8);
// print the char value
System.out.print("\nNext Byte Value: " + value1);
}
catch (IndexOutOfBoundsException e) {
System.out.println("\nindex is negative or "
+ "smaller than the buffer's "
+ "limit, minus seven");
System.out.println("Exception Thrown : " + e);
}
}
}
输出：
Original ByteBuffer:
1234.3456 2884.4444
Byte Value: 1234.3456
Next Byte Value: 2884.4444
示例 2：
// Java program to demonstrate
// getDouble() method
import java.nio.*;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// Declaring the capacity of the ByteBuffer
int capacity = 16;
// Creating the ByteBuffer
try {
// creating object of ByteBuffer
// and allocating size capacity
ByteBuffer bb = ByteBuffer.allocate(capacity);
// putting the double value in the bytebuffer
bb.asDoubleBuffer()
.put(1234.3456)
.put(2884.4444);
// rewind the Bytebuffer
bb.rewind();
// Declaring the variable
double c;
// print the ByteBuffer
System.out.println("Original ByteBuffer: ");
for (int i = 1; i <= capacity / 8; i++)
System.out.print(bb.getDouble() + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the double at this buffer's current position
// using getDouble() method
double value = bb.getDouble(0);
// print the char value
System.out.println("\n\nByte Value: " + value);
// Reads the char at this buffer's next position
// using getDouble() method
double value1 = bb.getDouble(9);
// print the char value
System.out.print("\nNext Byte Value: " + value1);
}
catch (IndexOutOfBoundsException e) {
System.out.println("\nindex is negative or"
+ " smaller than the buffer's"
+ " limit, minus seven");
System.out.println("Exception Thrown : " + e);
}
}
}
输出：
Original ByteBuffer:
1234.3456 2884.4444
Byte Value: 1234.3456
index is negative or smaller than the buffer's limit, minus seven
Exception Thrown : java.lang.IndexOutOfBoundsException
参考： https://docs.oracle.com/javase/9/docs/api/ Java/nio/ByteBuffer.html#getDouble-int-