int[] a = new int[]{1,2,3,4,5}; 
int[] b = new int[a.length]; 
System.arraycopy(a, 0, b, 0, a.length); 

public class Test{ 
    public static void main(String[] args){ 
        int[] a = new int[]{1,2,3,4,5}; 
        int[] b = new int[a.length]; //应该初始化成和a长度一样的数组
        
        copy(a, b); 
        
        for(int i=0; i<b.length; i++){ 
            System.out.println(b[i]); 
        } 
    } 

    public static int[] copy(int[] a, int[] b){ 
        for (int i=0; i<a.length; i++)
            b[i] = a[i];
        
        return b;
    } 
}

    public class Test{
        public static void main(String[] args){
        // a变量中的值的个数不能确定,所以b没办法new一个int[],
        // 就是你new 了一个够大的 new int[100],后面也还是同一个问题
        int[] a = new int[]{1,2,3,4,5};
        int[] b = new int[]{0,0,0,0,0};
        copy(a , b);
        for(int i = 0 ; i < 5 ; i++){
        System.out.println(b[i]);
        }

        }
        // 千万不要说改成b = copy(a)的形式
        public static void copy(int[] a, int[] b){
        //b = new int[]{0,0,0,0,0};
        System.arraycopy(a,0 , b ,0 , a.length);

        }

        }

public class Test {
    public static void main(String[] args) {
        int[] a = new int[] { 1, 2, 3, 4, 5 };
        int[] b = new int[a.length];
        new Test().copy(a, b);
        for (int i = 0; i < 5; i++) {
            System.out.println(b[i]);
            System.out.println(a[i]);
        }
    }

    public  void copy(int[] a, int[] b) {
        System.arraycopy(a, 0, b, 0, a.length);
    }
}