=true; } else{
boo=false; } } } public class ZuoYe4_3{ public static void main(String args[ ]){ SquareEquation equation1=new SquareEquation(4,5,1); SquareEquation equation2=new SquareEquation(3,5,-7); equation1.getRoots(); equation2.getRoots(); } } 4. import java.util.Scanner; class A{ int f(int m,int n){ if(m*n<0) { System.out.println("有负数,程序退出"); System.exit(0); } if(m
} int g(int m,int n){ int temp=a.f(m,n); return m*n/temp; } } public class ZuoYe4_4 { public static void main (String args[ ]) { Scanner reader=new Scanner(System.in); System.out.println("输入 2 个正整数,程序计算出它们的最大公约数和最小公倍数"); System.out.print("输入第一个整数:"); int m=reader.nextInt(); System.out.print("输入第二个整数:"); int n=reader.nextInt(); A a=new A(); B b=new B(); System.out.println(m+"和"+n+"的最大公约数是"+a.f(m,n)); System.out.println(m+"和"+n+"的最小公倍数是"+b.g(m,n)); } } 5. import java.applet.Applet; import java.awt.*; public class Example4_10 extends Applet { Button redbutton; public void init() { redbutton=new Button("我是一个红色的按钮"); redbutton.setBackground(Color.red); redbutton.setForeground(Color.white); add(redbutton); } }
第五章 作业题
1. import java.util.Scanner; class A { public int f(int m,int n) { if(m Scanner reader=new Scanner(System.in); System.out.println("输入 2 个整数,程序计算出它们的最大公约数和最小公倍数"); System.out.print("输入第一个整数:"); int m=reader.nextInt(); System.out.print("输入第二个整数:"); int n=reader.nextInt(); if(m*n<0) { System.out.println("有负数,程序退出"); System.exit(0); } System.out.printf("%d 和%d 的最大公约数是%d\n",m,n,a.f(m,n)); System.out.printf("%d 和%d 的最小公倍数是%d\n",m,n,b.f(m,n)); } } 2. . abstract class A{ public abstract void f(int x); public abstract void g(int x,int y); public abstract double h(double x); } class A1 extends A{ public void f(int x){ System.out.println(x); } public void g(int x,int y){ int z=x+y; System.out.println(z); } public double h(double x){ return x*x; } } class A2 extends A{ public void f(int x){ System.out.println("Hello:"+x); } public void g(int x,int y
){ int z=x-y;
System.out.println(z); } public double h(double x){ return Math.sqrt(x); } } class A3 extends A{ public void f(int x){ System.out.println("你好:"+x); } public void g(int x,int y){ double z=(double)x/y; System.out.println(z); } public double h(double x){ return 1/x; } } public class ZuoYe5_2{ public static void main(String args[ ]){ A a=new A1(); a.f(10); a.g(12,20); System.out.println(a.h(100)); a=new A2(); a.f(10); a.g(12,20); System.out.println(a.h(100)); a=new A3(); a.f(10); a.g(12,20); System.out.println(a.h(100)); } } 3. interface A{ public abstract void f(int x); public abstract void g(int x,int y); public abstract double h(double x);
} class A1 implements A{ public void f(int x){ System.out.println(x); } public void g(int x,int y){ int z=x+y; System.out.