String字符串常用方法總結

通過跑main方法來加深String印象

//String類爲不可變字符序列
//String類內部實質是數組private final char value[];
//字符串+數字返回仍是字符串
//new String的構造對象比直接賦值對象多創建一個對象，通過內存分析可得
public class TestString {

    public static void main(String[] args) {
        String s="abc";
        String s1=new String("def");
        String s2="abcdabcdab";
        String s3="a,s,cde";
        System.out.println(s.charAt(0));    //返回a
        System.out.println(s.indexOf("a")); //返回0
        System.out.println(s.lastIndexOf("c")); //返回2
        System.out.println(s2.indexOf("a",2));  //返回4
        System.out.println(s.concat(s1));   //返回abcdef
        System.out.println(s.contains(s1)); //返回false
        System.out.println(s.substring(0)); //返回abc
        System.out.println(s.substring(0, 1));  //返回a
        System.out.println(s2.replace('a','m' ));//返回mbcmbcdmb
        System.out.println(s2.endsWith("ab"));  //返回true
        System.out.println(s2.startsWith("a")); //返回true
        System.out.println(s1.getBytes());      //返回[B@15db9742
        String s4[]=s3.split(",");
        for(int i=0;i<s4.length;i++){
            System.out.print(s4[i]+"\t");       //返回a           s           cde
        }
        System.out.println();
        char c[]={'a','b','c'};
        System.out.println(String.copyValueOf(c));  //將字符數組轉爲字符串
        System.out.println(s.toUpperCase());        //返回ABC
        System.out.println(String.valueOf(50));     //返回字符串50
    }

}