Arrays.copyOf功能是實現陣列的複製，返回複製後的陣列。引數是被複制的陣列和複製的長度：

package setclass;

import java.util.Arrays;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

public class SetTest1 {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
        
  	  /*Array.copyof function test*/
        String[] arr=new String[5];
        String[] strs1={"123","234","345","456","789"};
        //String[] strs2=new String[2];//Two ways to state a array
        
        String[] str2=Arrays.copyOf(strs1, 3);
        String[] str3=Arrays.copyOf(strs1, 8);
        System.out.println();
        for(String ele:str2){
        	System.out.print(ele+";");
        	
        }
        System.out.println();
        for(String ele:str3){
        	System.out.print(ele+";");
        }

        int[] in={1,2,3,4,5};
        int[] int1=Arrays.copyOf(in,3);
        int[] int2=Arrays.copyOf(in,8);

        System.out.println();
        for(int ele:int1){
        	System.out.print(ele+";");
        	
        }
        System.out.println();
        for(int ele:int2){
        	System.out.print(ele+";");
        	
        }
  	
  	  }
}
 

123;234;345;
123;234;345;456;789;null;null;null;
1;2;3;
1;2;3;4;5;0;0;0;

說明：複製的長度大於被複制陣列的長度，則填充型別預設值，String得預設值是null,int的預設值是0。