DESKTOP-72IFJTH_20200909-赵亚军

1、问题：StringBuffer和StringBuilder一个表示线程安全的而另一个表示非线程安全的，什么时候应该用StringBuffer什么时候应该用StringBuilder??

2、例子：

StringBuffer buffer = new StringBuffer();
        
        System.out.println( "capacity : " + buffer.capacity() + " , length : " + buffer.length() );
        
        buffer.append( 100 );
        buffer.append( true );
        buffer.append( '\u0041' );
        buffer.append( (char)66 );
        buffer.append( "JPSB" );
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    public static void main(String[] args) {
        
        String s = "abc" ;
        
        StringBuilder builder = new StringBuilder( s );
        System.out.println( "length : " + builder.length() + " , capacity : " + builder.capacity() );
        
        String x = builder.toString(); 
        System.out.println( x == s );
    System.out.println( builder );
        
        builder.append( "你笑起来真好看" );
        System.out.println( builder );
        
        builder.delete( 0 ,  3 ) ;
        System.out.println( builder );

3、解决：

待解决