字符串基础

package zifuchuan;

import java.util.Date;

public class dsd {

public static void main(String[] args) {

//字符串

String str = "aa 醉了";   //字符串双引号       常用

char c = 'c';             //字符单引号

int j =1;

String str1 = new String ("a c bc bc f");   //少用

//连接字符 串    +

System.out.println("str+str1+j=" +str+str1+j);

//99乘法表

int []a= new int [5];

int l = a. length;  // 不带括号是属性

int g =str1.length();    //带括号是方法

System.out.println("str1.length()=" +g);

//查找
int sy =str1.indexOf("bc");

System.out.println("str1.indexOf(\"bc\") =" +sy);

int sy1 =str1.lastIndexOf("bc");

System.out.println("str1.indexOf(\"bc\") =" +sy1);

//取出字符

System.out.println("charAt=" + str1.charAt(2));

//截取字符串

System.out.println("substring= " +str1.substring(3));
System.out.println("substring= " +str1.substring(3,5));  //索引值5结束

//字符串的去除空格

String str3 = "  abc def gh  ";

System.out.println("str3.trim()=#" + str3.trim() + "#");//去空格

str3 = str3.trim();//保存去空格

System.out.println("str3.trim()=#" + str3 + "#");

//替换

str3 = str3.replace(" ","");

System.out.println("str3.replace()=#" + str3 + "#");

str3=str3.replace("bc","BC");

System.out.println("str3.replace()=#" + str3 + "#");

//判断字符串开始

System.out.println("str3.startsWith() =" +str3.startsWith("a"));
System.out.println("str3.endsWith() =" +str3.endsWith("a"));

String a1 = new String ("aaa");
String a2 = new String ("Aaa");
System.out.println("a1==a2="+a1==a2);        //==比较的是内存地址即a1与a2,不是各自包含的字符串

a1.equals(a2);

System.out.println("a1.equals(a2)=" +a1.equals(a2));// 区分大小写
System.out.println("a1.equalsIgnoreCase(a2)=" +a1.equalsIgnoreCase(a2));//不区分大小写

String b1 = "aaa";
String b2 = "aaa";
System.out.println("b1==b2="+(b1==b2));   //不建议使用

//按字典顺序比较  Unicode的值

System.out.println("compareTo=" +a1.compareTo(a2));//从第一位开始比较

//大小写转换

System.out.println("a1.toUpperCase=" +a1.toUpperCase());//转换大写
System.out.println("a1.toLowerCase=" +a1.toLowerCase());//转换小写

//字符串分割

String fg = "aa;bb;cc,ccc;ddd.ss";

String [] arr= fg.split(";");
String [] arr2 = fg.split(";|,");
String [] arr1 = fg.split(";" , 2 );

for (String f :arr)
{
System.out.println(f);

}

//格式化字符串  日期时间
// String.format(格式符,要被格式化的对象 );

Date dt =new Date();    //实例化日期，生成当前日期

System.out.println(String.format("%tF",dt));

System.out.println(String.format("%tT",dt));

System.out.println(String.format("%tR",dt));

System.out.println(String.format("%tF",dt)+" "+String.format("%tT",dt));

System.out.println("200的十六进制="+String.format("%x",200));

System.out.println("特定换行"+ String.format("%n")+"换行");

System.out.println("特定换行"+ "\n"+"换行");

StringBuilder strb = new  StringBuilder();

strb.append("abc");
strb.append("def");
strb.append("ghr");

strb.insert(2,"$$");
strb.delete(2, 5);
System.out.println("strb = " + strb.toString());

}

}