Java中的 ByteBuffer getLong() 方法及示例
得到长（）
Java.nio.ByteBuffer类的getLong()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long 值，然后将该位置加8。
句法：
public abstract long getLong()返回值：此方法返回缓冲区当前位置的 long 值。
抛出：此方法抛出BufferUnderflowException – 如果此缓冲区中剩余的字节少于四个。
以下是说明 getLong() 方法的示例：
示例 1：
// Java program to demonstrate
// getLong() 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 long value in the bytebuffer
bb.asLongBuffer()
.put(1233003)
.put(2292292);
// 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.getLong() + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the long at this buffer's current position
// using getLong() method
long value = bb.getLong();
// print the long value
System.out.println("\n\nByte Value: " + value);
// Reads the long at this buffer's next position
// using getLong() method
long value1 = bb.getLong();
// print the long value
System.out.print("\nNext Byte Value: " + value1);
}
catch (BufferUnderflowException e) {
System.out.println("\nException Thrown : " + e);
}
}
}
输出：
Original ByteBuffer:
1233003 2292292
Byte Value: 1233003
Next Byte Value: 2292292
示例 2：
// Java program to demonstrate
// getLong() 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 long value in the bytebuffer
bb.asLongBuffer()
.put(1233003)
.put(2292292);
// 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.getLong() + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the long at this buffer's current position
// using getLong() method
long value = bb.getLong();
// print the long value
System.out.println("\n\nByte Value: " + value);
// Reads the long at this buffer's next position
// using getLong() method
long value1 = bb.getLong();
// print the long value
System.out.print("\nNext Byte Value: " + value1);
// Reads the long at this buffer's next position
// using getLong() method
long value2 = bb.getLong();
}
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:
1233003 2292292
Byte Value: 1233003
Next Byte Value: 2292292
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#getLong–
getLong（整数索引）
ByteBuffer的getLong(int index)方法用于读取给定索引处的四个字节，根据当前字节顺序将它们组合成一个浮点值。
句法：
public abstract long getLong(int index)参数：此方法以索引（将从中读取字节的索引）作为参数。
返回值：此方法返回给定索引处的长值。
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getLong(int index)方法的示例：
示例 1：
// Java program to demonstrate
// getLong() 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 long value in the bytebuffer
bb.asLongBuffer()
.put(1233003)
.put(2292292);
// 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.getLong() + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the long at this buffer's current position
// using getLong() method
long value = bb.getLong(0);
// print the long value
System.out.println("\n\nByte Value: " + value);
// Reads the long at this buffer's next position
// using getLong() method
long value1 = bb.getLong(8);
// print the long 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:
1233003 2292292
Byte Value: 1233003
Next Byte Value: 2292292
示例 2：
// Java program to demonstrate
// getLong() 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 long value in the bytebuffer
bb.asLongBuffer()
.put(1233003)
.put(2292292);
// 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.getLong() + " ");
// rewind the Bytebuffer
bb.rewind();
// Reads the long at this buffer's current position
// using getLong() method
long value = bb.getLong(0);
// print the long value
System.out.println("\n\nByte Value: " + value);
// Reads the long at this buffer's next position
// using getLong() method
long value1 = bb.getLong(11);
// print the long 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:
1233003 2292292
Byte Value: 1233003
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#getLong-int-