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  • 随机数

    package com.hanqi1;
    
    import java.util.Random;
    
    public class Test {
    
        public static void main(String[] args)
        {
            String str1 = "字符串常量";      //字符串用""   字符用''
            
            String str2 = null;
            
            str2 = new String();
            
            str2 = new String("实例化字符串");
            
            char[] c = new char[]{'a','b','c'};
            
            str2 = new String(c);
            
            str2 = "fhospdowqdjshf";
            
            //字符集 
            
            
            System.out.println("str2.length=" + str2.length());
            
            System.out.println("str2=" + str2);
            
            //查找字符或字符串
            int in = str2.indexOf("bc");
            
            System.out.println("bc ="+in);  //输出的结果为索引值
            
            int la = str2.lastIndexOf("d");
            
            System.out.println("d = "+la);
            
            String newStr = str2.substring(5);
            
            newStr = str2.substring(5,6);
            
            System.out.println("substring()=" + newStr);
            
            str2 = " abcdds ";
            
            //去除前后空格
            System.out.println("去空格 ="+ str2.trim()+"后面");
    
            //查找替换
            System.out.println("查找替换空格="+str2.replace("","") + "后面");
            
            str2 = "abc,你好";
            
            System.out.println("查找替换空格="+str2.replace("abc","张三") + "");
            
            str2 = "abcde";
            
            //判断字符串开始和结束
            System.out.println("判断起始 = "+str2.startsWith("a"));
            
            System.out.println("判断起始 = "+(str2.indexOf("abc")==0));
        
            System.out.println("判断结束= "+str2.endsWith("de"));
            
            
            str1 = new String("abc");
            str2 = new String("abc");
            
            str2 = "ABC";
            
            System.out.println("判断字符串是否相等="+ (str1 == str2)+"str1="+str1.toUpperCase() +"str2 = "+str2.toLowerCase());
            
            
            System.out.println("判断字符串是否相等="+ str1.equals(str2));
            
            
            
            str2 = "abc#def#ghr#xyz";
            
            String[] array = str2.split("#");
            
            for (int i = 0;i<array.length;i++)
            {
                System.out.println(""+array[i]);
            }
            
            //数学运算
            System.out.println("四舍五入"+Math.round(123.556));
            
            //取上限值
            System.out.println("取上限值"+Math.ceil(123.456));
            
            System.out.println("取下限值"+Math.floor(123.456));
            
            System.out.println("PI="+Math.PI);
            
            
            //取随机数
            System.out.println("随机数="+Math.random());
            System.out.println("随机数="+Math.random());
            System.out.println("随机数="+Math.random());
            System.out.println("随机数="+Math.random());
            
            Random r = new Random();//用时间做种子
            
            r = new Random(1);//随机数种子
            
            System.out.println("随机数="+r.nextInt(100));
            System.out.println("随机数="+r.nextInt(100));
            System.out.println("随机数="+r.nextInt(100));
            System.out.println("随机数="+r.nextInt(100));
            System.out.println("随机数="+r.nextInt(100));
            System.out.println("随机数="+r.nextInt(100));
            System.out.println("随机数="+r.nextInt(100));
            
            
            
            
            
            
            
            
            
            
            
            
        }
        
    
    }
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  • 原文地址:https://www.cnblogs.com/ljxe/p/5052933.html
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