java---String类

Posted 2020-10-06 Constructor

package sad;
//String 类的常用方法
import java.util.Scanner;
public class ers {
    public static void main(String[] args)
    {   
      Factory.choose();    
}
}
class Factory
{
    static void choose()
    {
        int Choose=0;
        Scanner sc = new Scanner(System.in);
        while(true)
        {
        System.out.println("请输入您要的操作：");
        System.out.print("1:提取字符串中的某个字符\n2:字符串和数组相互转换\n3:判断是否包含某个字符串(查找)\n4:字符串替换\n5:截取字符串\n6:拆分字符串\n");
        Choose= sc.nextInt();
        switch(Choose)
        {
        case 1:
            new StringCharAt();
            break;
        case 2:
            new StringArray();
            break;
        case 3:
            new StringSearch();
            break;
        case 4:
            new StringReplace();
            break;
        case 5:
            new SubString();
            break;
        case 6:
            new StringSplit();
            break;
            default:
                break;
        }
        }
    }
}
class StringCharAt
{
    public StringCharAt() {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入字符串：");
        String str = sc.next();
        System.out.println("第零个字符是："+str.charAt(0));   //取出字符串中的某个字符
        System.out.println("第二个字符是："+str.charAt(2));
    }
}
class StringArray
{
    public StringArray()
    {
        Scanner sc = new Scanner(System.in);
        System.out.println("请输入字符串：");
        String str = sc.next();
        char data[] = str.toCharArray();    //字符串转数组
        System.out.println("该字符串转换为数组后为:");
        for(int i=0;i<data.length;i++)
        {
            System.out.println(data[i]+" ");
        }
        System.out.println("数组转换为字符串后为:");
        System.out.println(new String(data));   //数组转字符串
        System.out.println("从数组的某个字符开始截取某个长度的字符串:");
        System.out.println("请输入起始位置：");
        int start = sc.nextInt();
        System.out.println("请输入长度:");
        int length = sc.nextInt();
        System.out.println(new String(data,5,4));//起始点，长度
        System.out.println("____________________");
    }
}
class StringSearch
{
    public StringSearch() {
        // TODO Auto-generated constructor stub
        String str = "***hello**word";
        if(str.contains("hello"))     //判断是否包含某个字符串
        {
            System.out.println("包含指定的字符串");
        }
        if(str.indexOf("e")!=-1)   //从头开始判断是否存在指定字符 ，返回值是位置
        {
            System.out.println("字符串位置："+str.indexOf(‘e‘));
        }
        if(str.indexOf("e", 6)==-1)     //从指定位置开始向后查找是否存在某个字符
        {
            System.out.println("不存在");
        }
        if(str.lastIndexOf("e",12)==-1)    //从指定位置开始从后查找是否存在某个字符
        {
            System.out.println("不存在");
        }
        if(str.startsWith("*"))       //判断是否以某个字符开头
        {
            System.out.println("true");
        }
        if(str.startsWith("*",2))      //判断指定位置是否为某个字符或某一段字符
        {
            System.out.println("true");
        }
        if(str.endsWith("d"))       //判断是否由某个字符结束
        {
            System.out.println("true");
        }
        System.out.println("____________________");
    }
}
class StringReplace
{
    StringReplace()
    {  
        String str = "helloword";
        System.out.println(str.replaceAll("o", "***")); //将出现的某个字符所有的都替换
        System.out.println(str.replaceFirst("l", "_")); //将第一个出现的指定字符替换
        System.out.println("____________________");
    }
}
class SubString
{
    public SubString()
    {
        String str = "helloJava";
        System.out.println(str.substring(5)); //截取从指定位置到结尾的字符串
        System.out.println(str.substring(0,5));//截取指定位置的字符串
        System.out.println("____________________");
        
    }
}
class StringSplit
{   
    public StringSplit()
    {
    String str = "hello world hello java";
    String[] data = str.split(" ");
    for(int i=0;i<data.length;i++)
    {
        System.out.println(data[i]);
    }
    System.out.println("____________________");
    String data2[] = str.split(" ",3);
    for(int i=0;i<data2.length;i++)
    {
        System.out.println(data2[i]);
    }
    
    }
}