java8_api_字符串处理

字符串处理1

字符串处理2
    string的常用方法

package java_20180209_api_string;

public class StringDemo2 {

    public static void main(String[] args) {

        String s="abcdefcdefcdef";

        System.out.println(s.charAt(2));

//        String s1="";

        String s1=new String();

        System.out.println(s1.isEmpty());

        System.out.println(s1=="");

        System.out.println(s1.equals(""));

        System.out.println("".equals(s1));

        System.out.println(s.indexOf("cd",-3));

        System.out.println(s.lastIndexOf("cd"));

        System.out.println(s.substring(4, 7));

        System.out.println(" bce ".trim().length());

        System.out.println(s.replace('c', 'C'));

        System.out.println(s.replace("cd", "XX"));

        System.out.println(s.startsWith("dab"));

        System.out.println(s.endsWith("ef"));

        String[] result=s.split("de");

        for (String string : result) {

            System.out.println(string);

        }

        String result1=String.join("|", "java","is","cool");

        System.out.println(result1);

        System.out.println(String.valueOf(new char[]{'1','2','3'},1,2));

        char[] result2= {'a','a','a','d'};

        System.out.println(String.valueOf(result2, 1, 1));

        System.out.println("abc".compareTo("abcd"));

    }

}

字符串处理3
    StringBuffer与StringBuilder
    使用+拼接String的内部优化
            
    区别：String不可变，StringBuffer可变
    stringBuilder的常用方法
    
    使用+拼接String的内部优化
        String str="x"+"y"+12.56;
        其实被内部转换为String str=new StringBuilder().append("x").append("y").append(12.56).toString();

package java_20180209_api_string;

public class StringDemo3 {

    public static void main(String[] args) {

        StringBuilder builder=new StringBuilder();

        StringBuilder b=builder.append(11111).append("abcdefghi").append(1.2);

        System.out.println(b);

        System.out.println(b.length()+","+b.capacity());

        System.out.println(b.insert(2, "xxx"));

    }

}