java基础

Java123456__

于 2022-06-20 21:40:54 发布

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CC 4.0 BY-SA版权

文章标签：算法数据结构

本文链接：https://blog.youkuaiyun.com/Java123456__/article/details/125381183

本文介绍了两种方法来截取Java字符串中的内容，包括去除首尾空格后提取有效部分，并通过for和while循环实现。展示了字符串操作的基本实践和循环控制的运用。

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截取字符串


//截取字符串两边空格的第一种方式
        int i = 0;
        String str = "    H ell o  Wo rl d     ";
        int length = str.length() - 1;
        char[] arr = str.toCharArray();
        while (arr[i] == ' '){
            i++;

        }
        while (arr[length] == ' '){
            length--;
        }
        String sbu = str.substring(i, length + 1);
        System.out.println(substring);

//截取字符串两边空格的第二种方式
        int i = 0;
        String str = "       H ell o  Wo rl d        ";
        int length = str.length() - 1;

        char[] arr = str.toCharArray();
        while (arr[i] == ' ') {
            i++;
        }
        while (arr[length] == ' ') {
            length--;
        }
        System.out.println(i);
        System.out.println(length);
        String aa = "";
        for (int j = i; j <= length; j++) {
            aa = aa + arr[j];
        }
        System.out.println(aa);

for循环练习

package hm.day;

import javax.xml.transform.Source;
import java.nio.file.spi.FileSystemProvider;
import java.sql.SQLOutput;
import java.util.Scanner;
import java.util.concurrent.ForkJoinPool;

public class For1 {
    public static void main(String[] args) {
/*        for (int i = 1;  i < 9; i++) {
            System.out.println("Helloworld");

        }
        for (int j = 1; j<=5; j++){
            System.out.println(j);
        }
        System.out.println("---------------------------------");
        for (int k = 5; k>=1; k-- ){
            System.out.println(k);

                for (int i =1 ; i <= 5; i++) {
            if (i == 4){
                System.out.println("chong'lian");
            }
            System.out.println("断线重连第"+i+"次");
        }
                //累加
        int sum = 0;
        for (int i = 1; i <=5 ; i++) {
            System.out.println(i);
            sum = sum +i;
            //sum +=i;
        }
        System.out.println(sum);

     int sum = 0;
        for (int i = 1; i <= 100; i++) {
            if (i % 2==0){
                sum +=i;
            }
        }
        System.out.println(sum);



                Scanner sc = new Scanner(System.in);
        System.out.println("请输入第一个数字");
        int start = sc.nextInt();
        Scanner sc1 = new Scanner(System.in);
        System.out.println("请输入第二个数字");
        int end = sc.nextInt();
        int num = 0;
        for (int i = start; i <= end; i++) {
            if (i %3 ==0 && i %5 ==0) {
                num++;
                System.out.println(i);
            }
        }
        System.out.println("一共有"+num+"个数字满足条件");
        }*/



    }
}

while循环练习

package hm.day;

import com.sun.source.doctree.SummaryTree;

public class Wile {
    public static void main(String[] args) {
//        double i = 88444330;
//        double j = 0.1;
//        int count = 0;
//
//        while (j <k){
//            j = j *2;
//            count++;
//        }
//        System.out.println(count);

        int sum = 0;
        for (double k = 88444330; k >= 0.1; k--) {
            k = k/2;
            sum++;
        }
        System.out.println(sum);

    }
}