Java Array Operations

Array Extend & Set operation.java

// extend
System.arraycopy(names, 0, extended, 0, names.length);

// difference
objArray.removeAll(objArray2);
// intersection
objArray.retainAll(objArray2);
// union
Set<String> set = new HashSet<String>();
...
return set.toArray(result);

Array Fill.java

import java.util.*;

// Arrays.fill(arrayname,value)
// Arrays.fill(arrayname ,starting index ,ending index ,value)

Array Merge.java

String a[] = { "A", "E", "I" };
String b[] = { "O", "U" };
List list = new ArrayList(Arrays.asList(a));
list.addAll(Arrays.asList(b));
Object[] c = list.toArray();

//other method
import java.nio.*;

public class ConcatArrays {


    public static void main(String[] args) {
        int[] myNumbers=new int[]{1,2,3,4};
        int[] yourNumbers=new int[]{5,6,7};
        int[] theirNumbers=new int[]{8,9,0};

        //按需要分配buffer        
        IntBuffer intBuffer = IntBuffer.allocate(myNumbers.length+yourNumbers.length+theirNumbers.length);

        //放入到buffer        
        intBuffer.put(myNumbers);
        intBuffer.put(yourNumbers);
        intBuffer.put(theirNumbers);

        //得到合并后的数组        
        int[] allNumber = intBuffer.array();

        //显示合并后的数组        
        for (int i :allNumber ) {
            System.out.print(i);
            System.out.print(", ");
        }


        //各种数据原始类型都有buffer可用，非常方便        
        LongBuffer longBuffer = LongBuffer.allocate(10);
        DoubleBuffer doubleBuffer = DoubleBuffer.allocate(10);
        FloatBuffer floatBuffer = FloatBuffer.allocate(10);
        ByteBuffer byteBuffer = ByteBuffer.allocate(10);
        ShortBuffer shortBuffer = ShortBuffer.allocate(10);
        CharBuffer charBuffer = CharBuffer.allocate(10);
    }
}

Array Reverse.java

static void reverse(Integer a[])
    {
        Collections.reverse(Arrays.asList(a));
        System.out.println(Arrays.asList(a));
    }

contain & equal.java

// contain
ArrayList<String> objArray = new ArrayList<String>();
objArray.contains("common2");
objArray2.contains(objArray);// always false, because return index of objArray, i.e.,-1

//equal
Arrays.equals(ary, ary1);

Java array insert element.java

private static int[] insertElement(int original[],
   int element, int index) {
      int length = original.length;
      int destination[] = new int[length + 1];
      System.arraycopy(original, 0, destination, 0, index);
      destination[index] = element;
      System.arraycopy(original, index, destination, index
      + 1, length - index);
      return destination;
   }

sort,search,length,min&max.java

int array[] = { 2, 5, -2, 6, -3, 8, 0, -7, -9, 4 };
int fromindex=1,toindex=4;
Arrays.sort(array);
//sort from fromindex to toindex-1
Arrays.sort(array, fromIndex,toIndex);
//descending
Arrays.sort(array, Collections.reverseOrder());


int index = Arrays.binarySearch(array, 2);//2 is the value
int len = array.length;
int min = (int) Collections.min(Arrays.asList(array));