数组的Arrays 工具类

方法

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public class HelloWorld {     public static void main(String[] args){ //        //System.out.println("helloworld"); //        //int[] arr = new int[]{1,2,3}; //        //for ( //        int[] //        int[] ids = new int[5]; //        int p =4; //        for (int i=0;i<ids.length;i++ ){ //            ids[i] =p; //            p++; //            System.out.println(ids[i]); //        } //        Scanner scanner = new Scanner(System.in); //        System.out.println("请输入学生人数："); //        int number = scanner.nextInt(); //        int [] scores = new int[number]; //        System.out.println("请输入"+number+"个成绩"); //        for (int i =0;i<scores.length;i++){ //            scores[i] = scanner.nextInt(); //        } //        int maxScore = 0; //        for (int i=0;i<=scores.length;i++){ //            if(scores[i] > maxScore){ //                maxScore = scores[i]; //            } //        } //        char level; //        for (int i = 0;i<scores.length;i++){ //            if (maxScore-scores[i]<=10){ //                level ='A'; //            }else if (maxScore-scores[i]<=20){ //                level ='B'; //            }else if (maxScore-scores[i]<=30){ //                level ='C'; //            }else { //                level ='D'; //            } //            System.out.println("stubent" + scores[i] + ",grade is"+level); //        }//        Scanner scan = new Scanner(System.in);s //        Scanner scan = new Scanner(System.in); //        System.out.print("请输入学生个数："); //        int cx = scan.nextInt(); //        int[] Grades = new int[cx]; //        for (int i = 0 ;i <cx ;){ //            i++; //            System.out.print("请输入学生"+i+"成绩："); //            int sxi = scan.nextInt(); //            Grades[i-1] = sxi; //            //System.out.println(Grades[i-1]); //        } //        int masx =0; //        for (int i=0; i<Grades.length;i++){ //            if (masx<Grades[i]){ //                masx=Grades[i]; //            } //        } //        System.out.println("最高成绩"+masx); //        for (int i= 0;i<Grades.length;i++){ //            if(Grades[i]>=90){ //                System.out.println(Grades[i]+"优秀"); //            }else if(Grades[i]>=80){ //                System.out.println(Grades[i]+"好"); //            }else if(Grades[i]>=70){ //                System.out.println(Grades[i]+"良好"); //            } else if (Grades[i]>=60) { //                System.out.println(Grades[i]+"勉强及格"); //            }else{ //                System.out.println(Grades[i]+"继续努力"); //            } //        }         //判断两个数组是否相等         int[] cx = new int[]{1,2,3,4};         int[] cx2 = new int[]{1,2,8,5,3,9,4};         boolean is = Arrays.equals(cx,cx2);         System.out.println(is);         //输出数组信息         System.out.println(Arrays.toString(cx));         //将指定值填充数组中         Arrays.fill(cx,10);         System.out.println(Arrays.toString(cx));         //对数组排序         Arrays.sort(cx2);         System.out.println(Arrays.toString(cx2));           int[] cx3 = new int[]{-12,8,78,34,-87,72,91};         Arrays.sort(cx3);         System.out.println(Arrays.toString(cx3));         //根据数组元素找下标；提前排好序，否则会出错         int index = Arrays.binarySearch(cx3,78);         int index2 = Arrays.binarySearch(cx3,72);         System.out.println(index);         System.out.println(index2);       } } 测试 false [1, 2, 3, 4] [10, 10, 10, 10] [1, 2, 3, 4, 5, 8, 9] -7 5

　　数组常见异常

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public class HelloWorld {     public static void main(String[] args){         int[] cz = new int[]{1,2,3,4,5};         for (int i = 0 ;i<=cz.length;i++){             System.out.println(cz[i]);         }     } }       1 Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 5   地址越界异常 2     at com.chenxi.java.HelloWorld.main(HelloWorld.java:7) 3 4 5

　　空指针异常

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int [] cx = new int[]{2,8,6};         cx = null;         System.out.println(cx[0]);   1 Exception in thread "main" java.lang.NullPointerException 2     at com.chenxi.java.HelloWorld.main(HelloWorld.java:11) 3 4 5