java基础-String使用

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public static void main(String[] args) {// StringString str1 = "123";String str2 = "123";System.out.println(str1 == str2);// trueSystem.out.println(str1.equals(str2));//trueString str3 = new String("123");String str4 = new String("123");System.out.println(str3 == str4);// falseSystem.out.println(str3.equals(str4));//trueSystem.out.println(str1 == str3);// falseSystem.out.println(str1.equals(str3));// true//charAt()方法String s1 = "sun java";String s2 = "Sun Java";System.out.println(s1.charAt(2));//nSystem.out.println(s2.charAt(2));//n//indexof()方法//返回的是字符串的绝对位置，不会因从哪个位置开始寻找而改变原有的位置，除非在该位置后未找到而变成-1//在进行索引时字符与字符串功能一致System.out.println(s1.indexOf(97));//5System.out.println(s1.indexOf(97,2));//5System.out.println(s1.indexOf(97,6));//7System.out.println(s1.indexOf(97,5));//7//返回的是字符串的绝对位置，怒会用从哪个位置开始寻找而改变原有的位置，除非在该位置后未找到而变成-1System.out.println(s1.indexOf("java"));//4System.out.println(s1.indexOf("java",3));//4System.out.println(s1.indexOf("sun",2));//-1System.out.println(s1.indexOf('s',1));//-1System.out.println(s1.indexOf("sun"));//0System.out.println(s1.indexOf('s'));//0System.out.println(s1.equals(s2));//falseSystem.out.println(s1.equalsIgnoreCase(s2));//trueSystem.out.println(s1.toUpperCase());System.out.println(s2.toLowerCase());System.out.println(s1.replace("sun", "son"));System.out.println(s1.replace('u', 'o'));System.out.print((int)'j');String a = "Welcome to java";String b = "  sun  java  ";//startWith(),endWith()参数必须为字符串System.out.println(a.startsWith("W"));//System.out.println(a.startsWith('W'));报错System.out.println(a.endsWith("java"));System.out.println(a.toUpperCase());System.out.println(a.toLowerCase());System.out.println(a.trim());//"welcome to china"System.out.println(a.substring(5));System.out.println(a.substring(5,6)+"----");//m//从5开始，至6结束，包括5，不包括6System.out.println(a);//Welcome to javaString strj = new String();//一个空字符串System.out.println("+" + strj + "+");System.out.println("+++++++++++++++++");//关于 public static String valueOf(参数)char ch='c';String chStr=String.valueOf(ch);byte bt = 12;String btStr = String.valueOf(bt);short s = 12;String sStr = String.valueOf(s);int i = 12;String iStr = String.valueOf(i);long l = 12;String lStr = String.valueOf(l);float f = 12.0f;String fStr = String.valueOf(f);double d = 12;String dStr = String.valueOf(d);boolean bo = false;String boStr = String.valueOf(bo);//"false",长度为5System.out.println(chStr + "-" + chStr.length());//cSystem.out.println(btStr + "-" +btStr.length());System.out.println(sStr + "-" +sStr.length());System.out.println(iStr + "-" + iStr.length());System.out.println(lStr + "-" + lStr.length());System.out.println(fStr + "-" + fStr.length());//12.0--4System.out.println(d);//double型数据           输出 12.0System.out.println(dStr + "-" + dStr.length());//12.0--4   System.out.println(boStr + "-" + boStr.length());//false--5//split("")参数必须为字符串String str = "1,32,43,54,6532,34";String [] array = str.split(",");//String [] array = str.split(',');报错for(i = 0; i < array.length; i++) {System.out.println(array[i]);}}
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