11. The two arrays

First, the array of tools

Package com.atguigu.java; 

Import java.util.Arrays; 

/ * 
 * java.util.Arrays: array operation tools, many of which defines a method of operating an array 
 * 
 * 
 * / 
public  class ArraysTest {
     public  static  void main ( String [] args) { 
        
        // 1.boolean the equals (int [] A, int [] B): determining whether the two arrays are equal. 
        int [] of arr1 = new new  int [] {1,2,3,4 };
         int [] = arr2 is new new  int [] {1,3,2,4 };
         Boolean isEquals = that Arrays.equals (of arr1, arr2 is); 
        System.out.println (isEquals); // false
        
        // 2.String toString (int [] A): the information output array. 
        System.out.println (of Arrays.toString (of arr1)); 
        
            
        // 3.void Fill (int [] A, int Val): The specified value is filled into the array. 
        Arrays.fill (arr1,10 ); 
        System.out.println (of Arrays.toString (of arr1)); 
        

        // 4.void Sort (int [] A): sort the array. 
        Arrays.sort (arr2 is); 
        System.out.println (of Arrays.toString (arr2 is)); 
        
        // 5.int binarySearch (int [] A, int Key) 
        int [] = ARR3 new new  int [] {- 98, - 34,2,34,54,66,79,105,210,333 };
         int index = Arrays.binarySearch (ARR3, 210 );
         IF (index> = 0 ) {
            System.out.println(index);
        }else{
            System.out.println("未找到");
        }
        
        
    }
}

Second, the array of related algorithms

Package com.atguigu.java;
 / * 
 * test algorithms: find the value of the maximum array elements, minimum, average, sum and the like 
 * 
 * define a one-dimensional array of type int, containing 10 elements, respectively assigned random integer number, 
 * and the maximum value of all the elements and then, a minimum value, and the value of the average value and outputs it.    
 * Requirements: All randomized double-digit number. 
 * 
 * [10,99] 
 * formula: (int) (Math.random () * (99 - 10 +. 1) + 10) 
 * 
 * / 
public  class ArrayTest1 {
     public  static  void main (String [] args) {
         int [ ] = ARR new new  int [10 ]; 
        
        for ( int I = 0; I <arr.length; I ++ ) { 
            ARR [I] = ( int)(Math.random() * (99 - 10 + 1) + 10);
        }
        
        //遍历
        for(int i = 0;i < arr.length;i++){
            System.out.print(arr[i] + "\t");
        }
        System.out.println();
        
        //求数组元素的最大值
        int maxValue = arr[0];
        for(int i = 1;i < arr.length;i++){
            if(maxValue < arr[i]){
                maxValue = arr[i];
            }
        }
        System.out.println("最大值为：" + maxValue);
        
        // find the minimum value of the array element 
        int the minValue ARR = [0 ];
         for ( int I =. 1; I <arr.length; I ++ ) {
             IF (the minValue> ARR [I]) { 
                the minValue = ARR [I]; 
            } 
        } 
        System.out.println ( "minimum value is:" + the minValue);
         // sum of array elements required 
        int sUM = 0 ;
         for ( int I = 0; I <arr.length; I ++ ) { 
            sUM + = ARR [ I]; 
        } 
        System.out.println ( "sum:" +SUM);
         // average number of array elements required 
        int AvgValue = SUM / arr.length; 
        System.out.println ( "Mean is:" + AvgValue); 
    } 
}

Package com.atguigu.java;
 / * 
 * test algorithms: an array replication, reverse lookup (linear search, binary search) 
 * 
 * 
 * / 
public  class ArrayTest2 { 
    
    public  static  void main (String [] args) { 
        
        String [] ARR = new new String [] { "JJ", "DD", "the MM", "BB", "GG", "AA" }; 
        
        
        // copy an array (as distinct from the array variable assignment: arr1 = arr ) 
        String [] of arr1 = new new String [arr.length];
         for ( int I = 0; I <arr1.length; I ++ ) { 
            of arr1 [I] = ARR [I];
        } 
        
        // reverse the array
         //方法一：
//        for(int i = 0;i < arr.length / 2;i++){
//            String temp = arr[i];
//            arr[i] = arr[arr.length - i -1];
//            arr[arr.length - i -1] = temp;
//        }
        
        //方法二：
//        for(int i = 0,j = arr.length - 1;i < j;i++,j--){
//            String temp = arr[i];
//            arr[i] = arr[j];
//            arr[j] = temp;
//        }
        
        //遍历
        for(int i = 0;i < arr.length;i++){
            System.out.print(arr[i] + "\ T" ); 
        } 
        
        System.out.println (); 
        // Find (or search)
         // linear search: 
        String = dest "BB" ; 
        dest = "the CC" ; 
        
        Boolean isFlag = to true ; 
        
        for ( int I 0 =; I <arr.length; I ++ ) { 
            
            IF (dest.equals (ARR [I])) { 
                System.out.println ( "finds the specified element position:" + I); 
                isFlag = to false ;
                 BREAK ; 
            } 
            
        } 
        IF  (isFlag) {
            System.out.println ("Unfortunately, not found it!" ); 
            
        } 
        // binary searching :( familiar)
         // precondition: the array to be searched must be ordered. 
        int [] = arr2 is new new  int [] {- 98, -34,2,34,54,66,79,105,210,333 }; 
        
        int dest1 = -34 ; 
        dest1 = 35 ;
         int head = 0; // initial first index 
        int End arr2.length = -. 1; // initial index of the last 
        Boolean isFlag1 = to true ;
         the while (head <= end) { 
            
            int Middle = (end head +) / 2 ; 
            
            IF arr2 is [Middle]) {(dest1 == 
                System.out.println ( "finds the specified element position:" + Middle); 
                isFlag1 = to false ;
                 BREAK ; 
            } the else  IF (arr2 is [Middle]> dest1) { 
                End = Middle -. 1 ; 
            } the else { // arr2 is [Middle] <dest1 
                head = Middle +. 1 ; 
            } 

            
        } 
        
        IF (isFlag1) { 
            System.out.println ( "Unfortunately, not found it!" ); 
        } 
        
        
    } 
}