Java数组的遍历与求和知识点

public class OneArry{ 
 public static void main(String[] args) { 
  double[] num = {1.9, 2.9, 3.4, 3.5,10,-1}; 
  num[0]=new Double(2); //通过下标把1.9变为2.0
  double sum = 0; 
  for (int i = 0; i < num.length; i++) { //遍历
 	 System.out.println(num[i]);
 	 sum+=num[i]; //求和
  } 
  System.out.println("一维数组之和为 " + sum); 
 } 
 }

2.0
2.9
3.4
3.5
10.0
-1.0
一维数组之和为 20.8

public class TwoArry{ 
  public static void main(String[] args) {
  	int sum=0;
    int num [][] ={ 
        {1,2,3,4,5}, 
        {6,7,8,9,10}, 
        {11,12,13,14,15}, 
        {16,17,18,19,20}, 
        {21,22,23,24,25}} ;  
    System.out.println("输出二维数组:");
    num[0][0]=new Integer(100); //通过下标把数组里的1变为100
     for(int i=0;i<num.length;i++){ //遍历，排列
       for( int j=0;j<num[i].length;j++){ 
         System.out.print(num[i][j]+"\t");
         sum+=num[i][j]; //求和
        		} 
     System.out.println();
         }
     System.out.println("二维数组之和为："+sum);
    }  
}

输出二维数组:
100	2	3	4	5	
6	7	8	9	10	
11	12	13	14	15	
16	17	18	19	20	
21	22	23	24	25	
二维数组之和为：424

public class TwoArry{  
	 public static void main(String args[ ]){  
	     int[][]num=new int[5][5];                     
	     int count=1; //数组从1开始循环 
	     int sum=0;
	     for(int i=0;i<num.length;i++){  
	      for(int j=0;j<num[i].length;j++){
	        num[i][j]=count++; //count添加到数组里
	        sum+=num[i][j]; //求和
//	        System.out.println(num[i][j]); //打印出所有数组
	       }
	     }
	     System.out.println("二维数组之和为："+sum);
	     System.out.println("输出二维数组:"); 
	     for(int i=0;i<num.length;i++){ //进行排列 
	       for(int j=0;j<num[i].length;j++){  
	         System.out.print(num[i][j]+"\t");
	       }       
	       System.out.println();     
	   }  
	 }  
} 

二维数组之和为：325
输出二维数组:
1	2	3	4	5	
6	7	8	9	10	
11	12	13	14	15	
16	17	18	19	20	
21	22	23	24	25