JAVA语言基础练习题 ——总10题

题1：
打印出数组中每个数的三倍

package zuoye1;

public class zuoye11 {
	public static void main(String [] args){
		int [] a = {12,3,34,5,546,768,234,56};
		for(int i = 0 ; i 
题2：
 从键盘接收10个数逆序储存到一个数组中，再正序打印。
 
package zuoye1;

import java.util.Scanner;

public class zuoye12 {
	public static void main(String [] args){
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();
		int []a = new int [len];
		for(int i = len-1;i>-1; i--){
			a[i] = sc.nextInt();
		}
		for(int i = 0; i 
题3：
 输出数组中最大值最小值
 
package zuoye1;

import java.util.Scanner;

public class zuoye13 {
	public static void main(String [] args){
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();
		int []a = new int [len];
		int max = 0,min = 0;
		for(int i = len-1;i>-1; i--){
			a[i] = sc.nextInt();
			if(i == len-1){
				max = min = a[i];
			}
			else if(a[i]>max){
				max = a[i];
			}
			else if(a[i]>min&&a[i] 
题4：
 从键盘接收n个数储存到数组a中，将非0数储存到数组b中并打印。
 
package zuoye1;

import java.util.Scanner;

public class zuoye14 {
	public static void main(String [] args){
		Scanner sc = new Scanner(System.in);
		int len = sc.nextInt();
		int []a = new int [len];
		for(int i = 0;i 
题5：Random类
 给大小为100的数组每个位置随机填充1-100之间的数。
 
package zuoye1;

import java.util.Random;

public class zuoye15 {
	public static void main(String[] args){
		int a[] = new int[100];
		Random q = new Random();
		for(int i = 0;i<100;i++){
			a[i] = q.nextInt(99)+1;
		}
		for(int i = 0; i<100;i++){
			System.out.println(a[i]);
		}
	}
}

 
题6：String方法：
 ①：字符串转换为字符数组
 ②：int转换为String类型
 ③：字符串转换为大小写
 ④：判断字符数字
 ⑤：字符大小写转换
 ⑥：StringBuffer类
 
package zuoye1;

public class zuoye16 {
	public static void main(String [] args){
		String str = "abcd";
		System.out.println("将字符串转为字符数组后的结果");
		char [] charArray = str.toCharArray();
		for(int i = 0;i 
题7：
 逆序输出字符串，且将大写字母转换为小写，小写字母转换为大写。
 
package zuoye1;

import java.util.Scanner;

public class zuoye17 {
	public static void main(String [] args){
		Scanner sc = new Scanner(System.in);
		String q = sc.nextLine();
		char a[] = q.toCharArray();
		for(int i = a.length-1;i>-1;i--){
			if(Character.isLowerCase(a[i])){ 
				System.out.println(Character.toUpperCase(a[i]));
			}
			else {
				System.out.println(Character.toLowerCase(a[i]));
			}
		}
		sc.close();
	}
}

 
题8：
 通过特定字符分割字符串
 
package zuoye1;

public class zuoye18 {
	public static void main(String [] args){
		String s = "java@qweert";
		char a[] = s.toCharArray();
		StringBuffer q = new StringBuffer();
		StringBuffer w = new StringBuffer();
		int point = 0;
		for(int i = 0;i 
还可用String.split（）方法
 
package zuoye1;

public class zuoye18geng {
	public static void main(String [] args){
		String s = "java@qweert";
		String []a = s.split("@");
		for(int i = 0;i 
题9：
 在字符串中查找第二个子字符串的索引位置
 
package zuoye1;

public class zuoye19 {
	public static void main(String [] args){
		String s = "i love java i love java i love java";
		int a = s.indexOf("java");
		int w = s.indexOf("java",a+1)+1;
		System.out.println(w);
	}
}

 
题10：
 统计字符串数组中特定字符串出现的次数
 
package zuoye1;

public class zuoye110 {
	public static void main(String [] args){
		String a[] = {"java","c++","python","java","c++"
				,"python"
		};
		String w = "java";
		int n = 0;
		for(int i =0;i