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"));
    }

}