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📜  Java string和stringBuffer之间的差异

📅  最后修改于: 2020-09-25 14:56:44             🧑  作者: Mango

String和StringBuffer之间的区别

String和StringBuffer之间有许多区别。下面列出了String和StringBuffer之间的差异：

No. String StringBuffer
1) String class is immutable. StringBuffer class is mutable.
2) String is slow and consumes more memory when you concat too many strings because every time it creates new instance. StringBuffer is fast and consumes less memory when you cancat strings.
3) String class overrides the equals() method of Object class. So you can compare the contents of two strings by equals() method. StringBuffer class doesn’t override the equals() method of Object class.

String和StringBuffer的性能测试

public class ConcatTest{  
    public static String concatWithString()    {  
        String t = "Java";  
        for (int i=0; i<10000; i++){  
            t = t + "Tpoint";  
        }  
        return t;  
    }  
    public static String concatWithStringBuffer(){  
        StringBuffer sb = new StringBuffer("Java");  
        for (int i=0; i<10000; i++){  
            sb.append("Tpoint");  
        }  
        return sb.toString();  
    }  
    public static void main(String[] args){  
        long startTime = System.currentTimeMillis();  
        concatWithString();  
        System.out.println("Time taken by Concating with String: "+(System.currentTimeMillis()-startTime)+"ms");  
        startTime = System.currentTimeMillis();  
        concatWithStringBuffer();  
        System.out.println("Time taken by Concating with  StringBuffer: "+(System.currentTimeMillis()-startTime)+"ms");  
    }  
}

String和StringBuffer HashCode测试

正如您在下面给出的程序中看到的那样，当您连接字符串时，String返回新的哈希码值，但是StringBuffer返回相同的值。

public class InstanceTest{  
    public static void main(String args[]){  
        System.out.println("Hashcode test of String:");  
        String str="java";  
        System.out.println(str.hashCode());  
        str=str+"tpoint";  
        System.out.println(str.hashCode());  
           System.out.println("Hashcode test of StringBuffer:");  
        StringBuffer sb=new StringBuffer("java");  
        System.out.println(sb.hashCode());  
        sb.append("tpoint");  
        System.out.println(sb.hashCode());  
    }  
}