1.利用arraycope的方法

public class MergeArr {
    public static void main(String[] args) {
        int[] arr1 = {1,2,3,4,5,6};
        int[] arr2 = {7,8,9};
     	//合并完的数组
        int[] arr3 = new int[arr1.length + arr2.length];
        System.arraycopy(arr1, 0, arr3, 0, arr1.length);
        System.arraycopy(arr2, 0, arr3, arr1.length, arr2.length);
        System.out.println(Arrays.toString(arr3));
    }
   } 

2.将两数组合并 ，在排序

 public static void main(String[] args) {
        int[] arr1 = {1,2,3};
        int[] arr2 = {1,4,5};
       int[] arr3 = mergeArr(arr1,arr2);
       compareArr(arr3);
       for (int i =0;i<arr3.length;i++){
           System.out.println(arr3[i]+" ");
       }
    }
    public  static int[] mergeArr(int[] arr1,int[] arr2 ){
        int[] arr3 = new int[arr1.length+arr2.length];
        //将arr1 存入新数组
        for(int i =0;i<arr1.length;i++){
            arr3[i] = arr1[i];
        }
        //将arr2 存入新数组
        for(int i =0;i<arr2.length;i++){
            arr3[arr1.length+i] = arr2[i];
        }
        return arr3;
    }
    public static void compareArr(int[] arr ){
        for(int i =0;i<arr.length-1;i++){
            for(int j = 0;j<arr.length-i-1;j++){
                if(arr[j]>arr[j+1]){
                    int temp = arr[j];
                    arr[j] = arr[j+1];
                    arr[j+1] = temp;
                }
            }
        }
    }