JAVA练习题二

1．定义并任意输入一个数组a,包含10个元素.利用集合框架中的工具类(java.util.Arrays),完成: 1)对该数组排序后输出; 2)输入一个x,查询在数组中有没有该值;

package cn.whb.test03;

import java.io.IOException;
import java.util.Arrays;
import java.util.Scanner;



public class work01 {
    
    
	
	public static void main(String[] args) throws IOException {
    
    
		int[] a = {
    
    1,3,4,87,41,123,32,54,1124,23};
		
		Scanner scanner = new Scanner(System.in);
		// 排序
		Arrays.sort(a);
 		System.out.println(Arrays.toString(a));
 		// 查找
 		int c = scanner.nextInt(); // 输入
 		
 		int index = Arrays.binarySearch(a, c);
 		String s = index>=0? ("存在索引为: " + index) :("不存在");
 		System.out.println(s);
	}
}

2．在分别在HashSet和TreeSet的集合中填加五个人的名字，并输出其中的元素。

package cn.whb.test03;

import java.util.HashSet;
import java.util.Set;
import java.util.TreeSet;

public class work02 {
    
    

	public static void main(String[] args) {
    
    
		// 创建集合
		Set<Students> stus = new HashSet<>();
		// 添加元素
		stus.add(new Students("xiao ming"));
		stus.add(new Students("xiao li"));
		stus.add(new Students("xiao wang"));
		stus.add(new Students("xiao zhang"));
		stus.add(new Students("xiao mei"));	
		
		System.out.println(stus);
		
		Set<Students> stus2 = new TreeSet<>();
		stus2.add(new Students("da ming"));
		stus2.add(new Students("da li"));
		stus2.add(new Students("da wang"));
		stus2.add(new Students("da zhang"));
		stus2.add(new Students("da mei"));
		System.out.println(stus2);
		
		
	}
}

class Students implements Comparable<Students>{
    
    
	private String name;

	public Students(String name) {
    
    
		this.name = name;
	}
	
	

	public String getName() {
    
    
		return name;
	}



	public void setName(String name) {
    
    
		this.name = name;
	}
	
	public String toString() {
    
    
		return this.name;
	}


	// 实现compareTo接口,使自定义类型之间可以比较
	public int compareTo(Students o) {
    
    
		int c = this.name.compareTo(o.getName());
		if(c>0) {
    
    
			return 1;
		}else if(c<0) {
    
    
			return -1;
		}else {
    
    
			return 0;
		}
	}
}

3．将下面程序paint方法和main方法补充完整，使得执行类似如下的结果：

package cn.whb.test03;

import java.awt.Graphics;
import javax.swing.*;
public class Example6_1 extends JFrame{
    
    
  
  Example6_1(){
    
    
  	super("简单图形");
  	setDefaultCloseOperation(EXIT_ON_CLOSE);
  	setSize(500,500);
  	setVisible(true);
  }
  
  public void paint(Graphics g){
    
    
    g.drawRect(100, 100, 200, 200);
    g.fillOval(150, 150, 200, 200);
  }
  
  public static void main(String args[]){
    
    
  	new Example6_1();
  }
}