Java String类
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一,String类
1、字符串是一个特殊的对象。
2、字符串一旦初始化就不可以被改变。
String类就代表一个字符串,不可以被复写,因为它没有子类。
Demo:
1 package com.hpioneer.Demo; 2 3 /** 4 * @Description: String类 5 * @Author: HPioneer 6 * @CreateTime: 2018/5/7 11:13 7 * @File: Java_String of JavaProject in com.hpioneer.Demo 8 * @FullFileName: com.hpioneer.Demo.Java_String 9 * @Create By IntelliJ 10 * @Version: 1.0 11 */ 12 public class Demo_String{ 13 public static void main(String[] args) { 14 15 //字符数组转字符串 16 char[] Array = { ‘r‘, ‘u‘, ‘n‘, ‘o‘, ‘o‘, ‘b‘}; 17 String string = new String(Array); 18 System.out.println( string ); 19 System.out.println(string.length()); //长度 20 System.out.println("1、hello,".concat(string)); //拼接 21 System.out.println(2+ "、hello," + string); //拼接 22 System.out.printf("浮点型变量的值为 " +"%f, 整型变量的值为 " +" %d, 字符串变量的值为 " +"is %s" , 1.0, 1, "1.0");//格式化 23 System.out.println(); 24 25 String q = "a"; 26 String w = "b"; 27 String e = q + w; 28 String r = new StringBuffer().append(q).append(w).toString(); //字符串相加的实现就是Buffer进行append之后tostring 29 30 String a = "saff"; 31 String b = "saff"; 32 String c = new String("saff"); 33 System.out.println(a.equals(b)); // true 34 System.out.println(a.equals(c)); // true 35 } 36 37 }
二,StringBuffer类
Demo:
1 package com.hpioneer.Demo; 2 3 /** 4 * @Description: 5 * @Author: HPioneer 6 * @CreateTime: 2018/5/7 11:58 7 * @File: Demo_StringBuffer of JavaProject in com.hpioneer.Demo 8 * @FullFileName: com.hpioneer.Demo.Demo_StringBuffer 9 * @Create By IntelliJ 10 * @Version: 1.0 11 */ 12 public class Demo_StringBuffer { 13 public static void main(String[] args) { 14 15 /* StringBuffer s = new StringBuffer(); 16 System.out.println(s.length());//0 17 System.out.println(s.capacity());//16 初始容量 18 19 StringBuffer s1 = new StringBuffer(10); 20 System.out.println(s1.length());//0 21 System.out.println(s1.capacity());//10 22 23 StringBuffer s2 = new StringBuffer("asas"); 24 System.out.println(s2.length());//8 25 System.out.println(s2.capacity());//24 = 8+16 26 27 System.out.println(s2.append(true));//asastrue 28 s2.deleteCharAt(0); 29 s2.delete(0,3); 30 System.out.println(s2.append("dfdfdf"));//truedfdfdf 31 System.out.println(s2.append(100));//truedfdfdf100 32 System.out.println(s2.insert(4,"KK"));//trueKKdfdfdf100 33 System.out.println(s2.reverse());//001fdfdfdKKeurt 34 System.out.println(s2.replace(0,2,"111"));//1111fdfdfdKKeurt 35 System.out.println(s2.substring(2,5));//11f*/ 36 37 /*StringBuffer sb = new StringBuffer("heima"); 38 39 String s1 = new String(sb); //通过构造将StringBuffer转换为String 40 System.out.println(s1); 41 42 String s2 = sb.toString(); //通过toString方法将StringBuffer转换为String 43 System.out.println(s2); 44 45 String s3 = sb.substring(0, sb.length()); //通过截取子字符串将StringBuffer转换为String 46 System.out.println(s3);*/ 47 48 String s = "heima"; 49 System.out.println(s); 50 change(s); 51 System.out.println(s); 52 //System.out.println(s+="itca"); 53 System.out.println("---------------------"); 54 StringBuffer sb = new StringBuffer(); 55 sb.append("heima"); 56 System.out.println(sb); 57 change(sb); 58 System.out.println(sb); 59 60 61 } 62 63 public static void change(StringBuffer sb) { 64 sb.append("itcast"); 65 } 66 67 public static void change(String s) { 68 s += "itcast"; 69 } 70 71 }
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