java的基础

java

import java.util.ArrayList;
import java.util.Scanner;
import java.util.Arrays;
public class class01 {
    public static void main(String[] args) {

        Scanner input = new Scanner(System.in);
        String a = input.nextLine();
        System.out.println(a);
        int b = input.nextInt();
        System.out.println(b);
        double c = input.nextDouble();
        System.out.println(c);
        long long d =input.nextLong();
        System.out.println(d);
        char e = input.next().charAt(0);
        System.out.println(e);
        int [] arr = new int[10];
        for(int i =0;i<arr.length;i++){
            arr[i]=input.nextInt();
        }
        lable:
       for(int i =0;i<2;i++){
            System.out.println(i+"\t");
            for(int j =0;j<3;j++){
                System.out.print(j+"\t");
                for(int k =0;k<2 ;k++){
//                    break lable;
                    continue;
                }
            }
        }

        排序
        int[] numbers = {3, 1, 4, 1, 5, 9};
        Arrays.sort(numbers);
        System.out.println(Arrays.toString(numbers));

        反转
        List<Integer> number = new ArrayList<>(Arrays.asList(1, 2, 3, 4, 5));
        Collections.reverse(number);
        System.out.println(number);
        Collection<String>c =new ArrayList<>();
        for(int i=0;i<4;i++){
            String d =input.nextLine();
            c.add("d");
        }
    //添加元素
        Iterator<String> it = c.iterator();
        while(it.hasNext()){
            String s = it.next();
            if("b".equals(s)){
                //指向谁,那么此时就删除谁.
                it.remove();
            }
    }
}

java 中的二分查找

import java.util.Scanner;
import java.util.Arrays;
public class test2 {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int a = input.nextInt();
        int[] arr = new int[a];
        for (int i = 0; i < a; i++) {
            arr[i] = input.nextInt();
        }
        int target = input.nextInt();

        // 二分查找初始化
        int l = 0, r = a - 1;
        int mid =0;
        while (l <= r) {
            mid = (l + r) / 2;

            if (arr[mid] == target) {
                break;
            } else if (arr[mid] > target) {
                r = mid - 1;
            } else {
                l = mid + 1;
            }
        }
            System.out.println(mid);

    }
}