JavaSE 高级 第04节 StringBuffer类

package com.java1995;

public class TestStringBuffer {

    public static void main(String[] args) {
        StringBuffer sb = new StringBuffer();
        System.out.println(sb.capacity());

        StringBuffer sb2 = new StringBuffer("abc");
        System.out.println(sb2.capacity());

        StringBuffer sb3 = new StringBuffer(100);
        System.out.println(sb3.capacity());

        StringBuffer sb4 = new StringBuffer("Hello");
        sb4.append(",");
        sb4.append("world!\n");
        sb4.append("welcome to ");
        sb4.append("www.java1995.com");

        System.out.println(sb4.toString());
    }
}

package com.java1995;

public class TestStringBuffer2 {

    public static void main(String[] args) {
        StringBuffer sb = new StringBuffer("helloworld");
        System.out.println(sb);
        for (int i = 0; i < sb.length(); i++) {
            char c = sb.charAt(i);

            c = (char) (c - 32);
            sb.setCharAt(i, c);
        }
        System.out.println(sb);
    }
}

package com.java1995;

import java.util.Date;

public class TestStringBuffer3 {

    public static void main(String[] args) {
        // System.out.println(new Date());
        // String str="";
        // for(int i=0;i<100000;i++){
        // str+=i;
        // }
        // System.out.println(new Date());
        // 18秒
        System.out.println(new Date());
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < 100000; i++) {
            sb.append(i);
        }
        System.out.println(new Date());
    }
}