在千锋学习的第21天
不积跬步无以至千里,不积小流无以成江河!加油
今天我学习了包装类和String类
下面是String类以及包装类的一些习题
代码为:
package ques7;
import java.util.Scanner;
public class Test7 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("请输入数字:");
String str = input.next();
//方法一
int i1 = Integer.parseInt(str);
System.out.println(i1);
//方法二
Integer i2 = new Integer(str);
int i3 = i2.intValue();
System.out.println(i3);
Integer i4 = Integer.valueOf(str);
//int i5 = i4.intValue();
System.out.println(i4);
}
}
8.
答案为:ABC
package ques8;
public class TestStudent{
public static void main(String[] args){
Student stu1 = new Student( "tom" , 18);
System.out.println(stu1 + " " + 100);
System.out.println(100 + " " + stu1);
//System.out.println(stu1 + 100 + " " );
System.out.println(" " + 100 +stu1);
}
}
class Student{
private int age;
private String name;
public Student(){}
public Student(String name, int age){
this.name = name;
this.age = age;
}
public String toString(){
return name +" "+ age;
}
}
package ques11;
public class Test11 {
public static void main(String[] args) {
String email = "[email protected]";
System.out.println(email.substring(0,7));
}
}
package quse12;
public class Test12 {
public static void main(String[] args) {
String email = "[email protected]";
int a1 = email.indexOf("@");
int a2 = email.indexOf(".");
if(a1 != -1 && a2 != -1&& a1 < a2){
System.out.println("合格的邮箱");
}else{
System.out.println("不合格");
}
}
}
package ques13;
import java.util.UUID;
public class Test13 {
public static void main(String[] args) {
String str = UUID.randomUUID().toString();
String str1 = str.replace("-", "");
System.out.println(str1);
}
}
package ques14;
import java.util.Random;
public class Test14 {
public static void main(String[] args) {
Random random = new Random();
String str1 = "ABCDEFGHijklmn1234567";
StringBuilder str3 = new StringBuilder();
int a;
for(int i=0; i< 4;i++){
a = random.nextInt(str1.length());
str3.append(str1.charAt(a));
}
System.out.println(str3);
}
}
package ques15;
import java.util.Scanner;
public class Test15 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("请输入一串数字:");
String str = input.next();
int[] arr = new int[10]; //这个数组下标0-9正好对应了每个数次出现次数的存放位置
for(int i=0;i< str.length();i++){//先循环接受的字符串
char c = str.charAt(i);//然后将得到的下标经过charAt方法转换成字符
for(int j=0;j< arr.length;j++){//然后和整数数组下标挨个对应
if(c-48 == j){ //因为0-9字符在ASCLL里面是48-57
arr[j]++;
}
}
}
for(int i=0;i< arr.length;i++){
System.out.println(i+"出现了"+arr[i]);
}
}