整個區塊鏈透過鏈的迴圈進行驗證，以確保一個區塊的雜湊仍然與前一個區塊的雜湊匹配。

這是 SimpleBlockChain.java的 validate（）方法實現。

public
boolean
validate() {

String previousHash = 
null
;

for
(Block<T> block : chain) {

String currentHash = block.getHash();

if
(!currentHash.equals(previousHash)) {

return
false
;

}

previousHash = currentHash;

}

return
true
;

}

下面是模組中的方法。從事務列表中建立Merkle樹的java類。

public
List<String> merkleTree() {        

ArrayList<String> tree = 
new
ArrayList<>();

// Start by adding all the hashes of the transactions as leaves of the

// tree.

for
(T t : transactions) {

tree.add(t.hash());

}

int
levelOffset = 
0
; 
// Offset in the list where the currently processed

// level starts.

// Step through each level, stopping when we reach the root (levelSize

// == 1).

for
(
int
levelSize = transactions.size(); levelSize > 
1
; levelSize = (levelSize + 
1
) / 
2
) {

// For each pair of nodes on that level:

for
(
int
left = 
0
; left < levelSize; left += 
2
) {

// The right hand node can be the same as the left hand, in the

// case where we don't have enough

// transactions.

int
right = Math.min(left + 
1
, levelSize - 
1
);

String tleft = tree.get(levelOffset + left);

String tright = tree.get(levelOffset + right);

tree.add(SHA256.generateHash(tleft + tright));

}

// Move to the next level.

levelOffset += levelSize;

}

return
tree;

}

一整套基於Java開發的的區塊鏈系統

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