Java Api--arrays Class

1, Arrays class overview· A tool class that operates on an array. Provides functions such as sorting, finding and so on. 2. Member Methods· public static string ToString (Int[] a): in[] A can be changed to an array of other types, and the array is converted to a string · public static void sort (int[] a): Sorts arrays of various types in ascending order · public static int BinarySearch (int[] a,int key): Binary lookup of arrays of various types

 Public classArraysDemo01 { Public Static voidMain (string[] args) {//define an array        int[] arr = {24, 69, 80, 57, 13 }; //Public static string toString (int[] a) turns the array into a stringSystem.out.println ("Before sorting:" + arrays.tostring (arr));//before sorting: [ +, +, +--]//Public static void sort (int[] a) sorting an arrayArrays.sort (arr); System.out.println ("After sorting:" +arrays.tostring (arr));//after sorting: [[+]        int[] arr2 = {13, 24, 57, 69, 80}; //public static int BinarySearch (int[] a,int key) Two-point lookupSystem.out.println ("BinarySearch:" +arrays.binarysearch (arr2,57));//Binarysearch:2System.out.println ("BinarySearch:" +arrays.binarysearch (arr2,557));//binarysearch:-6 Return-(low+1)    }}

3. Arrays class Common method source detailed explanation

 Public StaticString toString (int[] a) Public Static voidSortint[] a) The bottom is a quick sort Public Static intBinarySearch (int[] A,intkey) Development principle: As long as the object, we must determine whether the object is null. Test code:int[] arr = {24, 69, 80, 57, 13 }; System.out.println ("Before sorting:" +arrays.tostring (arr)); Sort Source: Public StaticString toString (int[] a) {//A-arr--{ ------    if(A = =NULL)        return"NULL";//Description Array object does not exist    intIMax = a.length-1;//imax=4;    if(IMax = =-1)        return"[]";//the description array exists, but there are no elements. StringBuilder B =NewStringBuilder (); B.append (‘[‘);//"["     for(inti = 0;; i++) {b.append (a[i]);//"[ in the"        if(i = =IMax)//"[[A] , a.            returnB.append ('] '). toString (); B.append (", ");//"[The]    }}-----------------------------------------------------Test Code:int[] arr = {13, 24, 57, 69, 80}; System.out.println ("BinarySearch:" + arrays.binarysearch (arr, 577) ); BinarySearch Source: Public Static intBinarySearch (int[] A,intkey) {    //A-arr--{ -------//Key--577    returnBinarySearch0 (A, 0, A.length, key);}Private Static intBinarySearch0 (int[] A,intFromIndex,intToindex,intkey) {    //A-arr--{ -------//FromIndex--0//Toindex--5//Key--577                                                                      intlow = FromIndex;//low=0    intHigh = toIndex-1;//high=4     while(Low <=High ) {        intMid = (low + high) >>> 1;//mid=2,mid=3,mid=4        intMidval = A[mid];//midval=57,midval=69,midval=80        if(Midval <key) Low= mid + 1;//low=3,low=4,low=5        Else if(Midval >key) high= Mid-1; Else            returnMid//Key found    }    return-(low + 1);//key not found.}

Java Api--arrays Class