java 学习一 数字

//1.number    2.enum     3.format float

//学习了 整数和FLOAT的 计算 ，枚举的使用 。 小数的格式化


package com.linson;
import java.text.DecimalFormat;


enum enum_op 
{  
    add,minus,time,divide
} 

public class HelloWord 
{
    public static void main(String[] args) 
    {
        System.out.println("hello world");
        
        HelloWord mMainHelloWord=new HelloWord();
        enum_op[] allOps=enum_op.values();
        
        int a=2,b=3;
        for(int i=0;i<allOps.length;i++)
        {
            System.out.println(mMainHelloWord.NumberCaculate(a, b, allOps[i]));
            System.out.println(mMainHelloWord.NumberCaculate_float(a, b, allOps[i]));
        }
        
        //format float
        DecimalFormat tempDF=new DecimalFormat();
        tempDF.applyPattern("0.00");
        float tempret=mMainHelloWord.NumberCaculate_float(16, 3, enum_op.divide);
        System.out.println(tempDF.format(tempret));
    }
    
    public int NumberCaculate(int a,int b,enum_op operate)
    {
        int ret=0;
        
        switch (operate) 
        {
            case add:
                ret=a+b;
                break;
            case minus:
                ret=a-b;
                break;
            case time:
                ret=a*b;
                break;
            case divide:
                ret=a/b;
                break;
            default:
                break;
        }
        return ret;
    }
    
    public float NumberCaculate_float(float a,float b,enum_op operate)
    {
        float ret=0;
        
        switch (operate) 
        {
            case add:
                ret=a+b;
                break;
            case minus:
                ret=a-b;
                break;
            case time:
                ret=a*b;
                break;
            case divide:
                ret=a/b;
                break;
            default:
                break;
        }
        return ret;
    }
}