Java中Integer方法实例详解

public final class Integer extends Number implements Comparable<Integer> {
    // 类的成员变量和方法
}

public class crj {
    public static void main(String[] args) {
//        //Integer(int value):
//        Integer i1=new Integer(100);
//        System.out.println(i1);
//        //Integer(String s)
//        Integer  i2=new Integer("100");
//        System.out.println(i2);
//        static Integer valueOf(int i):返回表示指定的int值的Integer实例
//        static Integer valueOf(String s):返回一个保存指定值的Integer对象String
        Integer i1=Integer.valueOf(100);
        Integer i2=Integer.valueOf("100");
        System.out.println(i1);
        System.out.println(i2);
    }
}

public class crj {
    public static void main(String[] args) {
        //int->String
        int number = 100;
        //方法1
        String s1 = number + "";
        System.out.println(s1);
        //方法2   static String ValueOf(int i)
        String s2 = String.valueOf(number);
        System.out.println(s2);
        //String->int
        String s = "100";
        //方法1  String->Integer->int
        Integer i = Integer.valueOf(s);
        int x = i.intValue();
        System.out.println(x);
        //方法2 static int parseInt(String s)
        int y = Integer.parseInt(s);
        System.out.println(y);
    }
}

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;
import javax.swing.*;
public class crj {
    public static void main(String[] args) {
        JFrame jf = new JFrame();
        jf.setTitle("猜数字");
        jf.setSize(400, 300);
        jf.setDefaultCloseOperation(3);
        jf.setLocationRelativeTo(null);
        jf.setAlwaysOnTop(true);
        jf.setLayout(null);
        //产生数字
        Random r = new Random();
        int number = r.nextInt(100) + 1;
        //提示信息
        JLabel messageLable = new JLabel("系统产生了一个1~100之间的数字，请猜一猜");
        messageLable.setBounds(70, 50, 350, 20);
        jf.add(messageLable);
        //猜数字文本框
        JTextField numberFiled = new JTextField();
        numberFiled.setBounds(120, 100, 150, 20);
        jf.add(numberFiled);
        //猜数字按钮
        JButton guessButton = new JButton("我猜");
        guessButton.setBounds(150, 150, 100, 20);
        jf.add(guessButton);
        guessButton.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                //猜的数据不能为空
                String StringNumber = numberFiled.getText().trim();
                if (StringNumber.equals("")) {
                    JOptionPane.showMessageDialog(jf, "猜的数字不能为空");
                    return;
                }
                //每次根据数字给出提示
                int guessNumber = Integer.parseInt(StringNumber);
                if (guessNumber > number) {
                    JOptionPane.showMessageDialog(jf, "你猜的数字"+guessNumber+"大了");
                    numberFiled.setText("");
                }else if(guessNumber<number){
                    JOptionPane.showMessageDialog(jf,"你猜的数字"+guessNumber+"小了");
                    numberFiled.setText("");
                }else{
                    JOptionPane.showMessageDialog(jf,"恭喜你猜中了");
                }
            }
        });
        jf.setVisible(true);
    }
}