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try/catch位于循环内会对性能造成影响，下面测试代码中两个方法只是try/catch的位置不同，结果就会有较大差异

import java.util.ArrayList;

public class Test {
	public static void main(String[] args) {
		Test test = new Test();
		int size = 1000;
		test.method1(size);
		test.method2(size);
	}
	public void method1(int size){
		long start = System.currentTimeMillis();
		ArrayList al = new ArrayList();
		String str = null;
		try{
			for(int i=0; i<size; i++){
				str = "str" + i;
				al.add(str);
			}
		}catch(Exception e){

		}
		System.out.println("method1 total: " + 
		  (System.currentTimeMillis() - start));
	}
	public void method2(int size){
		long start = System.currentTimeMillis();
		ArrayList al = new ArrayList();
		String str = null;
		for(int i=0; i<size; i++){
			try{
				str = "str" + i;
				al.add(str);
			}catch(Exception e){

			}
		}		
		System.out.println("method2 total: " + 
		  (System.currentTimeMillis() - start));
	}
}

我机器上的结果:
method1 total: 0
method2 total: 15