1．按照封装模式，编写“电费管理类”Manager。包含：
1）2个私有属性：上月电表读数pre，本月电表读数cur。
2）2个构造方法：无参（初始化pre、cur均为0）；2个参数（初始化pre、cur的值）。
3）main方法
代码：
package class1;
import java.util.Scanner;
public class Manager {
private double pre,cur;
public Manager() {
pre=0;
cur=0;
}
public Manager(double pre,double cur) {
this.pre=pre;
this.cur=cur;
}
public float f() {
return (float)(cur-pre);
}
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
double a,b;
System.out.print("请输入上个月电表读数：");
a=sc.nextDouble();
System.out.print("请输入本月电表读数：");
b=sc.nextDouble();
Manager m=new Manager(a,b);
System.out.print("本月用了"+m.f()+"度电");
}
}运行截图：
代码：
package class1;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class MyFrame implements ActionListener{
JFrame f;
JPanel p;
JLabel l1,l2,l3;
JButton b1,b2;
JTextField t1;
JPasswordField w1;
public MyFrame() {
f=new JFrame("登入界面");
p=new JPanel();
l1=new JLabel("用户名");
l2=new JLabel("密 码");
l3=new JLabel();
b1=new JButton("登入");
b2=new JButton("重置");
t1=new JTextField(20);
w1=new JPasswordField(20);
f.setSize(280, 150);
f.setVisible(true);
f.setLayout(new BorderLayout());
f.add(p,BorderLayout.CENTER);
p.add(l1);
p.add(t1);
p.add(l2);
p.add(w1);
p.add(b1);
b1.addActionListener(this);
p.add(b2);
b2.addActionListener(this);
f.add(l3,BorderLayout.SOUTH);
}
public static void main(String[] args) {
new MyFrame();
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO 自动生成的方法存根
if(e.getSource()==b1) {
if(t1.getText().equals("1234")&&w1.getText().equals("1234")) {
l3.setText(" 登入成功！");
}else {
l3.setText(" 用户名或密码输入错误，请重试！");
}
}else {
t1.setText("");
w1.setText("");
l3.setText(null);
}
}
}运行截图：
3．按以下要求编写程序：
1）编写Animal接口，接口中声明run( ) 方法
2）定义Bird类和Fish类实现Animal接口
3）编写Bird类和Fish类的测试程序，并调用其中的run( )方法
代码：
package class1;
interface Animal {
void run();
}
class Bird implements Animal{
public void run() {
System.out.println("这是Bird中的run方法");
}
}
class Fish implements Animal{
public void run() {
System.out.println("这是Fish中的run方法");
}
}
public class Animals{
public static void main(String[] args) {
Bird b=new Bird();
Fish f=new Fish();
b.run();
f.run();
}
}运行截图：
代码：
package class1;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.*;
public class MyJFrame implements ActionListener{
String str1="",str2="",str3="",temp1,temp;
int n1=0,judge;
float f1,f2,f3;
JFrame f;
JPanel p1,p2;
JTextArea ta;
JButton[]b1;
JButton[]b2;
String[]b11= {"1","2","3",
"4","5","6",
"7","8","9",
"0","清空","退格",
".","="};
String[]b22= {"+","-","*","/"};
public MyJFrame() {
f=new JFrame("简易计算器");
p1=new JPanel();
p2=new JPanel();
ta=new JTextArea();
b1=new JButton[b11.length];
for(int i=0;i<b11.length;i++) {
b1[i]=new JButton(b11[i]);
b1[i].addActionListener(this);
p1.add(b1[i]);
}
b2=new JButton[b22.length];
for(int i=0;i<b22.length;i++) {
b2[i]=new JButton(b22[i]);
b2[i].addActionListener(this);
p2.add(b2[i]);
}
f.setSize(300,250);
f.setLayout(new BorderLayout());
f.setVisible(true);
f.add(ta,BorderLayout.NORTH);
f.add(p1,BorderLayout.CENTER);
f.add(p2,BorderLayout.EAST);
p1.setLayout(new GridLayout(5,3));
p2.setLayout(new GridLayout(4,1));
}
public static void main(String[] args) {
new MyJFrame();
}
@Override
public void actionPerformed(ActionEvent e) {
// TODO 自动生成的方法存根
if(e.getActionCommand()=="0") {
ta.append("0");
}
else if(e.getActionCommand()=="1") {
ta.append("1");
}
else if(e.getActionCommand()=="2") {
ta.append("2");
}
else if(e.getActionCommand()=="3") {
ta.append("3");
}
else if(e.getActionCommand()=="4") {
ta.append("4");
}
else if(e.getActionCommand()=="5") {
ta.append("5");
}
else if(e.getActionCommand()=="6") {
ta.append("6");
}
else if(e.getActionCommand()=="7") {
ta.append("7");
}
else if(e.getActionCommand()=="8") {
ta.append("8");
}
else if(e.getActionCommand()=="9") {
ta.append("9");
}
else if(e.getActionCommand()==".") {
ta.append(".");
}
else if(e.getActionCommand()=="清空") {
ta.setText(" ");
}
else {
while(e.getActionCommand()=="+") {
str1=ta.getText();
n1=str1.length();
ta.append("+");
judge=1;
break;
}
while(e.getActionCommand()=="-") {
str1=ta.getText();
n1=str1.length();
ta.append("-");
judge=2;
break;
}
while(e.getActionCommand()=="*") {
str1=ta.getText();
n1=str1.length();
ta.append("*");
judge=3;
break;
}
while(e.getActionCommand()=="/") {
str1=ta.getText();
n1=str1.length();
ta.append("/");
judge=4;
break;
}
while(e.getActionCommand()=="=") {
if(judge==1) {
str2=ta.getText();
str3=str2.substring(n1+1, str2.length());
f1=Float.parseFloat(str1);
f2=Float.parseFloat(str3);
f3=f1+f2;
ta.setText("");
ta.append(f3+"");
break;
}
else if(judge==2) {
str2=ta.getText();
str3=str2.substring(n1+1, str2.length());
f1=Float.parseFloat(str1);
f2=Float.parseFloat(str3);
f3=f1-f2;
ta.setText("");
ta.append(f3+"");
break;
}
else if(judge==3) {
str2=ta.getText();
str3=str2.substring(n1+1, str2.length());
f1=Float.parseFloat(str1);
f2=Float.parseFloat(str3);
f3=f1*f2;
ta.setText("");
ta.append(f3+"");
break;
}
else if(judge==4) {
str2=ta.getText();
str3=str2.substring(n1+1, str2.length());
f1=Float.parseFloat(str1);
f2=Float.parseFloat(str3);
f3=f1/f2;
ta.setText("");
ta.append(f3+"");
break;
}
}
}
temp1=ta.getText();
temp=temp1.substring(0, temp1.length()-1);
if(e.getActionCommand()=="退格") {
ta.setText(temp);
}
}
}运行截图:
原文：https://www.cnblogs.com/quan-2723365710/p/12163840.html