day09-10

Exchange positions of the two elements of the list:

int temp = arr [1]; // temp-- to third
ARR [. 1] = ARR [2];
ARR [2] = TEMP;
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Two heavy cycle:
number of control lines layer, inner layer to control the number of columns.
99 cycles for double printing multiplication table:
Package. 3;
public class ___ {print multiplication table the 2_1-th
 public static void main (String [] args) {
  for (int I =. 1; I <=. 9; I ++) {
   for (int. 1 = J; J <= I; J ++) {
    of System.out.print (J + "*" + I + "=" + I * + J "\ T");
   }
   System.out.println ();
  } 
 / / * 1 = 1 1
 // 2 1 = 2 * 2 * 2 = 4
 // 3 = 1 * 2 * 3 * 3 = 63 3 = 9
 @ 1 = 4 * 4 * 2 * 4 = 8 4 3 12 is. 4. 4 = * = 16  // Print (columns + "*" + the number of lines () + "=" ranks multiplication);  } } ----------------- -----------------
  

Copy List:
sequentially removed old elements in the list, to the new list are installed;
int [] oldArray =
{11,22,44,263,55,6,4,7}; int [] newArray = new int [oldArray.length ]; for (int I = 0; I <oldArray.length; I ++) { // sequentially removed old elements in the list, to the new list are installed newArray [I] = oldArray [I]; ------- ---------------------------
  

  

Sorting an array:
// arr operation. Sort.
Arrays.sort (arr); (Method)
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int max = a > b ? a : b;

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Two-dimensional array:
// three forms
int [] [] intArray;
  float floatArray [] [];
  Double [] doubleArray []
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Method, function - Syntax:
 access modifier return type function name (parameter list) {
           function body}
  public static void getArrayMax () {}
  void empty;

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迭代、遍历：
// 1:先取出小容器，
//2：然后再取小容器里面的元素

for (int i = 0; i < arr.length; i++) {
//   arr[i] 代表小容器。
   for(int j = 0;j<arr[i].length;j++) {
    System.out.print(arr[i][j]);
   }
   System.out.println();
  }

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查找某个列表中是否存在某个元素：
/**
* 查找某个列表中是否存在某个元素。
* 存在就提示存在，
* 不存在就提示不存在。
* 带参。无返回值。
* 1:参数列表。int []arr,int num
* 2:返回值类型。void
*/
 public static void findNum(int [] arr,int num) {
  for(int i =0;i<arr.length;i++) {
   if(arr[i] == num) {
    System.out.println("找到了");
    break;
   }
  }

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