30天学会JAVA—练习题(2021韩顺平)——Day5

1.代码

public class A01 {
   
	//属性
	double[] arr;
	double m;	
	
	//方法
	public double max(double[] arr){
   		
		for(int i = 0; i < arr.length ; i++){
   
			if(arr[i] >= m){
   
				m = arr[i];
			}
		}		
		return m;		
	}
	
	
	public static void main(String[] args) {
   
		A01 a = new A01();
		double[] arr = new double[]{
   1.2,3.2,0,1};
		
		System.out.println(a.max(arr));
	}
}

2.代码

public class A02 {
   
	public int find(char[] arr, char target){
   
		for(int i = 0; i < arr.length; i++){
   
			if(target == arr[i]){
   
				return i;
			}
		}
		return -1;
	}
	
	public static void main(String[] args) {
   
		A02 a = new A02();
		char[] arr = new char[]{
   'a','b','c'};
		System.out.println(a.find(arr, 'd'));		
	}
}

3.代码

public class Book {
   	
	public void updatePrice(String name, double price){
   
		System.out.println("书名为：" + name +" 原价格为：" + price);
		if(price <= 0){
   
			System.out.println("价格无效！");
			return;
		}else if(price > 150){
   
			price = 150;	
			System.out.println("书名为："+ name +" 修改后价格为：" + price);
		}else if(price > 100 && price <=150){
   
			price = 100;		
			System.out.println("书名为："+ name +" 修改后价格为：" + price);
		}
		
	}
	
	public static void main(String[] args) {
   
		Book b = new Book();
		b.updatePrice("java大法好", 0);
	}
}

4.代码

public class A03 {
   
	public int[] copyArr(int[] arr){
   
		int[] brr = new int[arr.length];
		for(int i = 0 ;i < arr.length; i++){
   
			brr[i] = arr[i];
		}		
		return arr;		
	}
	
	public static void main(String[] args) {
   
		A03 a = new A03();
		int[] arr = new int[]{
   1,4,5,7};
		System.out.println("原始数组为：" + Arrays.toString(arr));
		System.out.println("复制数组为：" + Arrays.toString(a.copyArr(arr)));
	}
}

5.代码

public class Circle {
   
	public double showC(double r){
   //周长
		double c = 2 * Math.PI * r;		
		return c;		
	}
	
	public double showS(double r){
   //面积
		double s =  Math.PI * r *r;		
		return s;		
	}
	
	public static void main(String[] args) {
   
		Circle cl = new Circle();
		System.out.println("周长为：" + cl.showC(1.0));
		System.out.println("面积为：" + cl.showS(1.0));
	}
}

6. 代码

public class Cale {
   
	int a;
	int b;
	public Cale(int a, int b){
   
		this.a = a;
		this.b = b;
	}
	
	public int showSum(){
   //和
		int sum = a + b;
		System.out.println("和为：" + sum);
		return sum;	

	}
	
	public int showSub(){
   //差
		int sub = a - b;
		System.out.println("差为：" + sub);
		return sub;		
	}
	
	public int showMul(){
   //积
		int mul = a * b;
		System.out.println("积为：" + mul);
		return mul;		
	}
	
	public double showDiv(){
   //商
		int div = 0;
		if(b == 0){
   
			System.out.println("除数为0，请重新输入");
		}else{
   
			div = a / b;
			System.out.println("商为：" + div);
			return div;	
		}
		return div;	
	}
	
	public static void main(String[] args) {
   
		Cale c1 = new Cale(12,4);
		System.out.println("第一个对象：12,4");
		c1.showSum();
		c1.showSub();
		c1.showMul();
		c1.showDiv();
		
		Cale c2 = new Cale(12,0);
		System.out.println("第二个对象：12,0");
		c2.showSum();
		c2.showSub();
		c2.showMul();
		c2.showDiv();
	}
}

7.代码

public class Dog {
   
	String name;
	String color;
	int age;
	
	public void show(String name, String color, int age){
   
		System.out.println(this.name = name);
		System.out.println(this.color = color);
		System.out.println(this.age = age);
	}
	
	public static void main(String[] args) {
   
		Dog d = new Dog();
		d.show("哈士奇", "黑白", 5);
	}
}