字符串代码

package com.hanqi;

import java.util.Random;

public class ZFC {
    public static void main(String[] args) {
        
    String str1 = "字符串常量";
    
    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 = ("asdsajkljfadaskllkjflj");
    
    //字符集
    
    //str2 = new String(bytes);
    
    System.out.println("str2.length = " + str2.length() );

    System.out.println("str2 = " + str2 );

    //查找字符或字符串
    
    int in = str2.indexOf("bb");
    
    System.out.println("bb = " + in);
    
    int  la = str2.lastIndexOf("d");
    
    System.out.println("d = " + la);
    
    String newStr = str2.substring(5 , 6);
    
    System.out.println("sunstraung() = " + newStr);
        
    str2 = "  abcdad  ";
    
     //去除前后两格
    System.out.println("去空格 = " + str2.trim()+"后面");
    
    
    //查找  替换
    
    str2.replace(" ", "");
    
    System.out.println("查找替换设备 = " +str2.replace(" ", "")+"后面");

    str2 = "abc,不好";
    
    System.out.println("查找替换 = " +str2.replaceFirst("abc ", "张三")+"");

    str2 = "abcde";
    //判断字符串开始和结束
    
    str2.startsWith("a");
    
    System.out.println("判断起始 = " + str2.startsWith("a"));

    System.out.println("判断起始" + (str2.indexOf("acb")== 0));

    str2.endsWith("f");
    
    System.out.println("判断结束 = " + str2.endsWith("f"));
    
    str1 = new String("abc");
    
    str2 = new String("abc");
    
    System.out.println("判断字符串相等=" + (str1 == str2));
    
    System.out.println("判断字符串相等=" + (str1.equals(str2)));

    str1 = "abc";
    
    str2 = "abc";
    
    System.out.println("判断字符串相等a=" + (str1 == str2));
    
    System.out.println("判断字符串相等b=" + (str1.equals(str2)));
    
    System.out.println("str1 = " + str1.toUpperCase());
    
    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(123.456));
    //取上限值
    System.out.println("取上限值="+Math.ceil(123.456));
    //取下限值
    System.out.println("取下限值="+Math.floor(123.456));
    System.out.println("PI="+Math.PI);
    
    //随机数
    System.out.println("随机数="+Math.random());
    
    Random r= new Random();//时间作为种子
    //r=new Random(1);//随机数种子，出来的结果是不变的
    
    System.out.println("Random随机数="+r.nextInt(1000));
    System.out.println("Random随机数="+r.nextInt(1000));
    System.out.println("Random随机数="+r.nextInt(100));
    System.out.println("Random随机数="+r.nextInt(100));
    System.out.println("Random随机数="+r.nextInt(10));
    }

}