String StringBuffer StringBuilder(增删查改)

小灰灰 2021-11-16 06:14 277阅读 0赞

package com.qf.test;
    
    public class StringBuilderTest {
    
    	public static void main(String[] args) {
    		//fun1();
    		//testTime();
    		test();
    
    	}
    	/*
    	 * String   StringBuffer   StringBuilder   比较
    	 */
    	//String
    	public static void test01() {
    		String string="";
    		for (int i = 0; i <10000; i++) {
    			string+="hello";
    		}
    	}
    	//StringBuffer
    	public static void test02() {
    		StringBuffer buffer=new StringBuffer();
    		for (int i = 0; i < 1000000; i++) {
    			buffer.append("hello");
    		}
    	}
    	//StringBuilder
    	public static void test03() {
    		StringBuilder builder=new StringBuilder();
    		for (int i = 0; i <1000000; i++) {
    			builder.append("hello");
    		}
    	}
    	public static void test() {
    		long start = System.currentTimeMillis();
    		
    		test03();
    		long end = System.currentTimeMillis();
    		System.out.println(end-start);
    	}
    	public static void testTime() {
    		long start = System.currentTimeMillis();
    		int sum=0;
    		for (int i = 0; i < 1000000000; i++) {
    			sum+=1;
    		}
    		long end = System.currentTimeMillis();
    		System.out.println(end-start);
    	}
    	/*
    	 * StringBuilder
    	 * 线程不同步 执行速度块 线程不安全
    	 * 在某一个位置插入字符串
    	 * 字串反转
    	 * 字串拼接
    	 * 删除
    	 */
    	public static void fun1() {
    		StringBuilder stringBuilder=new StringBuilder("结果:");
    		System.out.println(stringBuilder);
    		System.out.println(stringBuilder.length());
    		
    		//增
    		stringBuilder.append(true);
    		stringBuilder.append('汗');
    		stringBuilder.append("天地人");
    		stringBuilder.append(new Object());
    		System.out.println(stringBuilder);
    		
    		//删除
    		stringBuilder.delete(11, stringBuilder.length());
    		System.out.println(stringBuilder);
    		stringBuilder.deleteCharAt(7);
    		System.out.println(stringBuilder);
    		
    		//改
    		stringBuilder.setCharAt(7, '笑');
    		System.out.println(stringBuilder);
    		
    		//插入insert
    		stringBuilder.insert(7, "朱元璋");
    		System.out.println(stringBuilder);
    		
    		//查
    		System.out.println(stringBuilder.indexOf("朱元璋"));
    		
    		//反转
    		StringBuilder reverse = stringBuilder.reverse();
    		System.out.println(reverse);
    	}
    
    }