java基础-数组

public class Example3 {
    public static void main(String[] args) {
        int[] month = new int[]{31,28,31,30,31,30,31,31,30,30,30,31};
        for(int i = 0 ; i < 12; i++){
            System.out.println((i+1)+"月份的天数是"+month[i]+"天");
        }
    }
}

public class Trap {
    public static void main(String[] args) {
        int b[][] = new int[][]{{0},{1,2,3},{4,5,6}};
        for(int i = 0 ; i < b.length ; i++){
            for(int k = 0 ; k < b[i].length ; k++){
                System.out.print(b[i][k]);
            }
            System.out.println();
        }
    }
}

import java.util.Arrays;
public class Swap {
    public static void main(String[] args) {
        int[] a = new int[5];
        Arrays.fill(a,8);
        for(int i = 0 ; i < a.length ; i++){
            System.out.println("第"+i+"个元素是" + a[i]);
        }
    }
}

import java.util.Arrays;
public class Displace {
    public static void main(String[] args) {
        int arr[] = new int[]{45,12,25,23};
        Arrays.fill(arr,1,2,3);
        for(int i = 0 ; i < arr.length ; i++){
            System.out.println("第"+i+"个元素是" + arr[i]);
        }
    }
}

import java.util.Arrays;
public class Taxis {
    public static void main(String[] args) {
        int arr[] = new int[]{15,8,2,23,36};
        Arrays.sort(arr);
        for(int i = 0 ; i < arr.length ; i++){
            System.out.println("第"+i+"个元素是" + arr[i]);
        }
    }
}

import java.util.Arrays;
public class Copy {
    public static void main(String[] args) {
        int arr[] = new int[]{15,8,2,236};
        int newarr[] = Arrays.copyOf(arr,5);

        for(int i = 0 ; i < newarr.length ; i++){
            System.out.println("第"+i+"个元素是" + newarr[i]);
        }
    }
}

import java.util.Arrays;
public class repeact {
    public static void main(String[] args) {
        int arr[] = new int[]{15,8,2,236};
        int newarr[] = Arrays.copyOfRange(arr,0,3);

        for(int i = 0 ; i < newarr.length ; i++){
            System.out.println("第"+i+"个元素是" + newarr[i]);
        }
    }
}

import java.util.Arrays;
public class Example4 {
    public static void main(String[] args) {
        int arr[] = new int[]{15,8,2,236};
        Arrays.sort(arr);
        int index = Arrays.binarySearch(arr,15);
        System.out.println("2的索引位置是："+index);
    }
}

import java.util.Arrays;
public class Rakel {
    public static void main(String[] args) {
        String str[] = new String[]{"b","ff","cccc","aa"};
        Arrays.sort(str);
        int index = Arrays.binarySearch(str,0,2,"b");
        System.out.println("ff的索引位置是："+index);
    }
}