Java Collections - Arrays.binarySearch() Examples

Java Collections Java Java API 

Class:

java.util.Arrays

Methods:

These methods searches the specified array for the specified value using the binary search algorithm.

public static int binarySearch(long[] a,
                               long key)

public static int binarySearch(long[] a,
                               int fromIndex,
                               int toIndex,
                               long key)

public static int binarySearch(int[] a,
                               int key)

public static int binarySearch(int[] a,
                               int fromIndex,
                               int toIndex,
                               int key)

public static int binarySearch(short[] a,
                               short key)

public static int binarySearch(short[] a,
                               int fromIndex,
                               int toIndex,
                               short key)

public static int binarySearch(char[] a,
                               char key)

public static int binarySearch(char[] a,
                               int fromIndex,
                               int toIndex,
                               char key)

public static int binarySearch(byte[] a,
                               byte key)

public static int binarySearch(byte[] a,
                               int fromIndex,
                               int toIndex,
                               byte key)

public static int binarySearch(double[] a,
                               double key)

public static int binarySearch(double[] a,
                               int fromIndex,
                               int toIndex,
                               double key)

public static int binarySearch(float[] a,
                               float key)

public static int binarySearch(float[] a,
                               int fromIndex,
                               int toIndex,
                               float key)

public static int binarySearch(Object[] a,
                               Object key)

public static int binarySearch(Object[] a,
                               int fromIndex,
                               int toIndex,
                               Object key)

public static <T> int binarySearch(T[] a,
                                   T key,
                                   Comparator<? super T> c)

public static <T> int binarySearch(T[] a,
                                   int fromIndex,
                                   int toIndex,
                                   T key,
                                   Comparator<? super T> c)

Examples

package com.logicbig.example.arrays;

import java.util.Arrays;

public class BinarySearchExample {

    public static void main(String... args) {
        int[] arr = {1, 2, 3, 4, 6, 7};
        int i = Arrays.binarySearch(arr, 6);
        System.out.println(i);
    }
}

Output

4

package com.logicbig.example.arrays;

import java.util.Arrays;

public class BinarySearchExample2 {


    public static void main(String... args) {
        int[] arr = {1, 2, 3, 4, 6, 7};
        int i = Arrays.binarySearch(arr, 2, 5, 6);
        System.out.println(i);
    }
}

Output

4

package com.logicbig.example.arrays;

import java.util.Arrays;

public class BinarySearchExample4 {


    public static void main(String... args) {
        char[] arr = {'a', 'b', 'c', 'd', 'e', 'f'};
        int i = Arrays.binarySearch(arr, 'd');
        System.out.println(i);
    }
}

Output

3

package com.logicbig.example.arrays;

import java.util.Arrays;

public class BinarySearchExample5 {


    public static void main(String... args) {
        String[] arr = {"one", "two", "four", "three"};
        //arr must be in sorted order for binarySearch to work
        Arrays.sort(arr);
        int i = Arrays.binarySearch(arr, "three");
        System.out.println(i);
    }
}

Output

2

package com.logicbig.example.arrays;

import java.util.Arrays;
import java.util.Comparator;

public class BinarySearchExample6 {


    public static void main(String... args) {
        String[] arr = {"1", "2", "3", "4"};

        Arrays.sort(arr, Comparator.reverseOrder());

        int i = Arrays.binarySearch(arr, "4", Comparator.reverseOrder());
        System.out.println(i);

        i = Arrays.binarySearch(arr, "1", Comparator.reverseOrder());
        System.out.println(i);
    }
} 

Output

0
3

package com.logicbig.example.arrays;

import java.util.Arrays;

public class BinarySearchExample7 {


    public static void main(String... args) {
        MyClass[] arr = {MyClass.of("3"), MyClass.of("2"),
                MyClass.of("1"), MyClass.of("4")};

        Arrays.sort(arr);

        int i = Arrays.binarySearch(arr, MyClass.of("4"));
        System.out.println(i);

        i = Arrays.binarySearch(arr, MyClass.of("2"));
        System.out.println(i);
    }

    private static class MyClass implements Comparable<MyClass> {
        private String myStr;

        static MyClass of(String str) {
            MyClass myClass = new MyClass();
            myClass.myStr = str;
            return myClass;
        }

        public String getMyStr() {
            return myStr;
        }

        @Override
        public int compareTo(MyClass o) {
            return myStr.compareTo(o.myStr);
        }
    }
} 

Output

3
1