Java DoubleBuffer compareTo()方法及示例

java.nio.DoubleBuffer 类的 compareTo() 方法是用来比较一个缓冲区和另一个缓冲区。两个双缓冲区通过比较它们的剩余元素序列进行比较，不考虑每个序列在其相应缓冲区中的起始位置。一对浮动元素的比较是通过调用Double.compare(double, double)进行的，除了-0.0和0.0被认为是相等的。Double.NaN被这个方法认为是等于自己，并且大于所有其他的双倍值（包括Double.POSITIVE_INFINITY）。双重缓冲区不能与任何其他类型的对象相提并论。

语法

public int compareTo(DoubleBuffer that)

参数： 该方法需要 一个双缓冲区对象 作为参数，该缓冲区将与之进行比较。

返回值： 如果这个缓冲区小于、等于或大于给定的缓冲区，该方法返回一个 负整数、零或正整数 。

下面是说明compareTo()方法的例子。

例子1： 当两个DoubleBuffer都相等时。

// Java program to demonstrate
// compareTo() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        // Declaring the capacity of the db
        int capacity1 = 3;
  
        // Creating the DoubleBuffer
        try {
  
            // creating object of Doublebuffer db
            // and allocating size capacity
            DoubleBuffer db = DoubleBuffer.allocate(capacity1);
  
            // putting the value in db
            db.put(9.56);
            db.put(7.61);
            db.put(4.61);
  
            // revind the Double buffer
            db.rewind();
  
            // print the DoubleBuffer
            System.out.println("DoubleBuffer db: "
                               + Arrays.toString(db.array()));
  
            // creating object of Doublebuffer db1
            // and allocating size capacity
            DoubleBuffer db1 = DoubleBuffer.allocate(capacity1);
  
            // putting the value in db1
            db1.put(9.56);
            db1.put(7.61);
            db1.put(4.61);
  
            // revind the Double buffer
            db1.rewind();
  
            // print the DoubleBuffer
            System.out.println("DoubleBuffer db1: "
                               + Arrays.toString(db1.array()));
  
            // compare both buffer and store the value into integer
            int i = db.compareTo(db1);
  
            // if else condition
            if (i == 0)
                System.out.println("\nboth buffer are lexicographically equal");
            else if (i >= 0)
                System.out.println("\ndb is lexicographically greater than db1");
            else
                System.out.println("\ndb is lexicographically less than db1");
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("Exception throws : " + e);
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("Exception throws : " + e);
        }
    }
}

输出:

DoubleBuffer db: [9.56, 7.61, 4.61]
DoubleBuffer db1: [9.56, 7.61, 4.61]

both buffer are lexicographically equal

例2： 当这个DoubleBuffer大于传递的DoubleBuffer时

// Java program to demonstrate
// compareTo() method
  
import java.nio.*;
import java.util.*;
  
public class GFG {
  
    public static void main(String[] args)
    {
  
        // Declaring the capacity of the db
        int capacity1 = 3;
  
        // Creating the DoubleBuffer
        try {
  
            // creating object of Doublebuffer db
            // and allocating size capacity
            DoubleBuffer db = DoubleBuffer.allocate(capacity1);
  
            // putting the value in db
            db.put(9.56);
            db.put(7.61);
            db.put(4.61);
  
            // revind the Double buffer
            db.rewind();
  
            // print the DoubleBuffer
            System.out.println("DoubleBuffer db: "
                               + Arrays.toString(db.array()));
  
            // creating object of Doublebuffer db1
            // and allocating size capacity
            DoubleBuffer db1 = DoubleBuffer.allocate(capacity1);
  
            // putting the value in db1
            db1.put(8.56);
            db1.put(7.61);
            db1.put(4.61);
  
            // revind the Double buffer
            db1.rewind();
  
            // print the DoubleBuffer
            System.out.println("DoubleBuffer db1: "
                               + Arrays.toString(db1.array()));
  
            // compare both buffer and store the value into integer
            int i = db.compareTo(db1);
  
            // if else condition
            if (i == 0)
                System.out.println("\nboth buffer are lexicographically equal");
            else if (i >= 0)
                System.out.println("\ndb is lexicographically greater than db1");
            else
                System.out.println("\ndb is lexicographically less than db1");
        }
  
        catch (IllegalArgumentException e) {
            System.out.println("Exception throws : " + e);
        }
  
        catch (ReadOnlyBufferException e) {
            System.out.println("Exception throws : " + e);
        }
    }
}

输出:

DoubleBuffer db: [9.56, 7.61, 4.61]
DoubleBuffer db1: [8.56, 7.61, 4.61]

db is lexicographically greater than db1