D0712

package com.hp.d;

import java.util.Scanner;

//字符串“打劫！我有枪”，“枪”是敏感词汇，替换为“*”，并输出打印
public class demo1 {

    public static void main(String[] args) {

        String string = "打劫！我有枪！！";
        String ss = "枪";
        String[] s = ss.split("");
        for (int i = 0; i < s.length; i++) {
            string = string.replace(s[i],"*");
        }
        System.out.println(string);

    }
}

打劫！我有*！！

Process finished with exit code 0

package com.hp.d;
//字符串“北京欢迎你”，替换字符为“郑州欢迎你们”，并输出打印
public class demo2 {
    public static void main(String[] args) {
        String a= "北京欢迎你";
        String b= "郑州欢迎你们";
        String s = a.replaceAll(a, b);
        System.out.println(s);


    }
}

郑州欢迎你们

Process finished with exit code 0

package com.hp.d;
//字符串“面向对象是以对象为核心..编程思想”，获取并第一个下标和最后一个下标的字符，并输出打印
public class demo3 {

    public static void main(String[] args) {
        String s = "面向对象是以对象为核心..编程思想";
        for (int index = 0; index <= s.length() - 1; index++) {
            String w = s.substring(index, index + 1);
            String a = s.substring( s.length()-1,index+s.length());
            System.out.println("第一个下标字符是：" + w);
            System.out.println("最后一个下标字符值是：" + a);
            break;
        }

    }
}

第一个下标字符是：面
最后一个下标字符值是：想

Process finished with exit code 0

package com.hp.d;
//将double类型的数据3.1415926转为字符串
public class demo4 {

    public static void main(String[] args) {
        double d = 3.1415926;
       String s = String.valueOf(d);
         System.out.println(s+"是"+s.getClass().getName());


    }
}

3.1415926是java.lang.String

Process finished with exit code 0

package com.hp.d;
//判断一个字符串是否为空，如果为空，对其赋值，如果不为空，获取字符的个数并打印第一个字符
import java.util.Scanner;
public class demo5 {
    public void  gaaaa(String s ) {
        if (s == null || s.length() == 0 || s == " ") {
            System.out.println("字符串为空");
            System.out.println("为其赋值");
            Scanner a = new Scanner(System.in);
            String sss = a.nextLine();
            System.out.println(sss);
        } else {
            System.out.println("长度不为空");
            char ac = s.charAt(0);
            System.out.println("长度为" + s.length() + "第一个字符为" +ac);

        }
    }
}

package com.hp.d;

public class Test {
    public static void main(String[] args) {
        demo5 d = new demo5();
        String a = "";
        String b = "qwert";
        d.gaaaa(a);;
        d.gaaaa(b);
    }
}

字符串为空
为其赋值
pp
pp
长度不为空
长度为5第一个字符为q

Process finished with exit code 0

package com.hp.d;
//判断a在字符串abca中的位置，如果第一次出现的位置和最后一次出现的位置相同，则替换为*
public class demo6 {
    public static void main(String[] args) {
        String sa = "abca";
        int a1 = (sa.indexOf("a")+1);
        String aa1 = Integer.toString(a1);
        int aa = (sa.lastIndexOf("a")+1);
        String aa2 = Integer.toString(aa);
        System.out.println("a的位置为："+aa1);
        System.out.println("a最后的位置为："+aa2);
        if (aa1.equals(aa2)){
            aa2 = "*";
            System.out.println(sa.replace("a",aa2));
        }
        System.out.println("----------------------------------");
    }
}

a的位置为：1
a最后的位置为：4
----------------------------------

public class demo7 {
    public static void main(String[] args) {

        //int->包装类
        int i =1;
        Integer i1 = new Integer(i);
        //包装类->int
        Integer a = 1;
        int b =  a.intValue();

        //int->String
        int c = 1;
        String d = String.valueOf(c);
        //String->int
        String e = "1";
        int f = new Integer(e);

        //String->包装类
        String s = "123";
        Integer s1 =  Integer.valueOf(s);
        //包装类->String
        Integer ss= 1;
        String sss = Integer.toString(ss);
    }
}